Vulnerable Systems:
* Microsoft Windows 2000 Service Pack 4
* Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service Pack 2
* Microsoft Windows XP Professional x64 Edition
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service Pack 1
* Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft Windows Server 2003 with SP1 for Itanium-based Systems
* Microsoft Windows Server 2003 x64 Edition
* Microsoft Windows 98, Microsoft Windows 98 Second Edition (SE), and Microsoft Windows Millennium Edition (Me) Review the FAQ section of this bulletin for details about these operating systems.
* Internet Explorer 5.01 Service Pack 4 on Microsoft Windows 2000 Service Pack 4 Download the update
* Internet Explorer 6 Service Pack 1 on Microsoft Windows 2000 Service Pack 4 or on Microsoft Windows XP Service Pack 1 Download the update
* Internet Explorer 6 for Microsoft Windows XP Service Pack 2 Download the update
* Internet Explorer 6 for Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service Pack 1 Download the update
* Internet Explorer 6 for Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft Windows Server 2003 with SP1 for Itanium-based Systems Download the update
* Internet Explorer 6 for Microsoft Windows Server 2003 x64 Edition Download the update
* Internet Explorer 6 for Microsoft Windows XP Professional x64 Edition Download the update
* Internet Explorer 6 Service Pack 1 on Microsoft Windows 98, on Microsoft Windows 98 SE, or on Microsoft Windows Millennium Edition Review the FAQ section of this bulletin for details about this version.
Exception Handling Memory Corruption Vulnerability - CVE-2006-2218:
A remote code execution vulnerability exists in the way Internet Explorer handles exceptional conditions. As a result, system memory may be corrupted in such a way that an attacker could execute arbitrary code if a user visited a specially crafted Web site. An attacker who successfully exploited this vulnerability could take complete control of an affected system.
Mitigating Factors for Exception Handling Memory Corruption Vulnerability - CVE-2006-2218:
* In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content or advertisements could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to persuade users to visit the Web site, typically by getting them to click a link in an e-mail message or instant messenger message that takes users to the attacker's Web site.
* An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
* The Restricted sites zone helps reduce attacks that could try to exploit this vulnerability by preventing Active Scripting from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, they user could still be vulnerable to this issue through the Web-based attack scenario.
By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML e-mail messages in the Restricted sites zone. Additionally Outlook 2000 opens HTML e-mail messages in the Restricted sites zone if the Outlook E-mail Security Update has been installed. Outlook Express 5.5 Service Pack 2 opens HTML e-mail messages in the Restricted sites zone if Microsoft Security Bulletin MS04-018 has been installed.
Note While it cannot be ruled out that this vulnerability could be used in an exploit without Active Scripting, it significantly increases the chances of a successful exploit. As a result, this vulnerability has been given a severity rating of Critical.
* By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode mitigates this vulnerability in the e-mail vector because reading e-mail messages in plain text is the default configuration for Outlook Express. See the FAQ section for this security update for more information about Internet Explorer Enhanced Security Configuration.
Workarounds for Exception Handling Memory Corruption Vulnerability - CVE-2006-2218:
Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.
Note While it cannot be ruled out that this vulnerability could be used in an exploit without Active Scripting, it significantly increases the chances of a successful exploit. As a result, this vulnerability has been given a severity rating of Critical.
* Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone
You can help protect against this vulnerability by changing your settings to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone. To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and then click Custom Level.
4. Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.
5. Click Local intranet, and then click Custom Level.
6. Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.
7. Click OK two times to return to Internet Explorer.
Note Disabling Active Scripting in the Internet and Local intranet security zones may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly.
Impact of Workaround: There are side effects to prompting before running Active Scripting. Many Web sites that are on the Internet or on an intranet use Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use Active Scripting to provide menus, ordering forms, or even account statements. Prompting before running Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone .
Add sites that you trust to the Internet Explorer Trusted sites zone.
After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.
To do this, follow these steps:
1. In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.
2. In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.
3. If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.
4. In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.
5. Repeat these steps for each site that you want to add to the zone.
6. Click OK two times to accept the changes and return to Internet Explorer.
Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and *.update.microsoft.com (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.
* Set Internet and Local intranet security zone settings to High to prompt before running ActiveX Controls and Active Scripting in these zones
You can help protect against this vulnerability by changing your settings for the Internet security zone to prompt before running ActiveX controls and Active Scripting. You can do this by setting your browser security to High.
To raise the browsing security level in Microsoft Internet Explorer, follow these steps:
1. On the Internet Explorer Tools menu, click Internet Options.
2. In the Internet Options dialog box, click the Security tab, and then click the Internet icon.
3. Under Security level for this zone, move the slider to High. This sets the security level for all Web sites you visit to High.
Note If no slider is visible, click Default Level, and then move the slider to High.
Note Setting the level to High may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly even with the security setting set to High.
Impact of Workaround: There are side effects to prompting before running ActiveX Controls and Active Scripting. Many Web sites that are on the Internet or on an intranet use ActiveX or Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX Controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX Controls or Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX Controls or Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone
Add sites that you trust to the Internet Explorer Trusted sites zone.
After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.
To do this, follow these steps:
1. In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.
2. In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.
3. If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.
4. In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.
5. Repeat these steps for each site that you want to add to the zone.
6. Click OK two times to accept the changes and return to Internet Explorer.
Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and *.update.microsoft.com (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.
FAQ for Exception Handling Memory Corruption Vulnerability - CVE-2006-2218: What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could remotely take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.
What causes the vulnerability?
Internet Explorer allows objects to register exception handlers that may not properly handle certain conditions. Unsafe exception handling can cause memory corruption resulting in remote code execution.
What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to exploit this vulnerability through Internet Explorer and then persuade a user to view the Web site. This can also include Web sites that accept or host user-provided content or advertisements, and compromised Web sites. These Web sites could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to persuade users to visit the Web site, typically by getting them to click a link in an e-mail message or in an Instant Messenger request that takes users to the attacker's Web site. It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.
Could this vulnerability be exploited through e-mail?
This vulnerability could not be exploited automatically through e-mail or while viewing e-mail messages in the preview pane while using Outlook or Outlook Express. Customers would have to click a link that would take them to a specially crafted Web site, or open an attachment that could exploit the vulnerability.
What systems are primarily at risk from the vulnerability?
This vulnerability requires a user to be logged on and visiting a Web site for any malicious action to occur. Therefore, any systems where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from this vulnerability.
What does the update do?
The update removes the vulnerability by changing the way that Internet Explorer does exception handling. Specifically, exception handlers are removed from Internet Explorer with this update. These exception handlers were previously removed from Internet Explorer 7 and Windows Vista.
What might the removal of these exception handlers result in?
With the removal of these exception handlers, exceptions from objects that do not handle their own exception, which were previously caught within the Internet Explorer process may now result in application faults. These application faults could cause Internet Explorer to fail. The object or software where the application fault occurs now needs to either address the cause of the application fault or handle its own exception.
What can I do to prevent these application faults? Microsoft Security Bulletin MS06-023: Vulnerability in Microsoft JScript Could Allow Remote Code Execution (917344) addresses the cause of the application fault in JScript. Other objects, software, or Web application where application faults may occur as a result of the changes made in Microsoft security bulletin MS06-021 now needs to either address the cause of the application fault or handle its own exception.
What is exception handling and how can I implement it?
Robust code anticipates and handles exceptions. Exceptions occur when a program executes abnormally because of conditions outside the program's control. Certain operations, including object creation and file input/output, are subject to failures that go beyond errors. Out-of-memory conditions, for example, can occur even when your program is running correctly. For more information about exception handling see the product documentation:
When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.
Note This security update also includes updates for an application fault reported in to us through Microsoft Error Reporting Service. We actively analyze all error reports and prioritize them based on the number of customers affected by the application fault covered in the error report. This application fault is the same as the application fault called out in the public report of the non-exploitable variant of the vulnerability addressed in this security bulletin as Exception Handling Memory Corruption Vulnerability - CVE-2006-2218 .
This application fault has been discussed as CVE-2006-1992 and a subsequent public post also discussed the exception handling aspect. It is important to note that the application fault in and of itself only will cause Internet Explorer to fail, the vulnerability addressed in this security bulletin must be used for an exploit to occur.
When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.
HTML Decoding Memory Corruption Vulnerability - CVE-2006-2382:
A remote code execution vulnerability exists in the way Internet Explorer decodes specially crafted UTF-8 encoded HTML. An attacker could exploit the vulnerability by constructing a specially crafted Web page that could potentially allow remote code execution if a user visited the specially crafted Web site. An attacker who successfully exploited this vulnerability could take complete control of an affected system.
Mitigating Factors for HTML Decoding Memory Corruption Vulnerability - CVE-2006-2382:
* In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content or advertisements could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to persuade users to visit the Web site, typically by getting them to click a link in an e-mail message or instant messenger message that takes users to the attacker's Web site.
* An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
* By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode mitigates this vulnerability in the e-mail vector because reading e-mail messages in plain text is the default configuration for Outlook Express. See the FAQ section of this security update for more information about Internet Explorer Enhanced Security Configuration.
Workarounds for HTML Decoding Memory Corruption Vulnerability - CVE-2006-2382:
Microsoft has tested the following workarounds. Although these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.
* Read e-mail messages in plain text format if you are using Outlook 2002 or a later version, or Outlook Express 6 SP1 or a later version, to help protect yourself from the HTML e-mail attack vector.
Microsoft Outlook 2002 users who have applied Office XP Service Pack 1 or a later version and Microsoft Outlook Express 6 users who have applied Internet Explorer 6 Service Pack 1 or a later version can enable this setting and view e-mail messages that are not digitally signed or e-mail messages that are not encrypted in plain text only.
Digitally signed e-mail messages or encrypted e-mail messages are not affected by the setting and may be read in their original formats. For more information about how to enable this setting in Outlook 2002, see Microsoft Knowledge Base Article 307594.
Impact of Workaround: E-mail messages that are viewed in plain text format will not contain pictures, specialized fonts, animations, or other rich content. Additionally:
*The changes are applied to the preview pane and to open messages.
*Pictures become attachments so that they are not lost.
*Because the message is still in Rich Text or HTML format in the store, the object model (custom code solutions) may behave unexpectedly.
FAQ for HTML Decoding Memory Corruption Vulnerability - CVE-2006-2382: What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could remotely take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.
What causes the vulnerability?
When Internet Explorer handles specially crafted UTF-8 encoded HTML it may corrupt system memory in such a way that an attacker could execute arbitrary code.
What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site or HTML e-mail message that is designed to exploit this vulnerability through Internet Explorer and then persuade a user to view the Web site or HTML e-mail message. This can also include Web sites that accept user-provided content or advertisements, Web sites that host user-provided content or advertisements, and compromised Web sites. These Web sites could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to persuade users to visit the Web site, typically by getting them to click a link in an e-mail message or in an Instant Messenger request that takes users to the attacker's Web site. It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.
What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user is logged on and reading HTML e-mail messages or that a user is logged on and visits a Web site for any malicious action to occur. Therefore, any systems where HTML e-mail messages are read or where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from this vulnerability.
What does the update do?
The update removes the vulnerability by modifying the way that Internet Explorer decodes UTF-8 encoded HTML.
When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.
When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.
ActiveX Control Memory Corruption Vulnerability - CVE-2006-2383:
A remote code execution vulnerability exists in the DXImageTransform.Microsoft.Light ActiveX control if passed unexpected data. An attacker could exploit the vulnerability by constructing a specially crafted Web page that could potentially allow remote code execution if a user visited the specially crafted Web site. An attacker who successfully exploited this vulnerability could take complete control of an affected system.
Mitigating Factors for ActiveX Control Memory Corruption Vulnerability - CVE-2006-2383:
* In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content or advertisements could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to persuade users to visit the Web site, typically by getting them to click a link in an e-mail message or instant messenger message that takes users to the attacker's Web site.
* An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
* The Restricted sites zone helps reduce attacks that could try to exploit this vulnerability by preventing ActiveX Controls from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, the use could still be vulnerable to this issue through the Web-based attack scenario.
By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML e-mail messages in the Restricted sites zone. Additionally Outlook 2000 opens HTML e-mail messages in the Restricted sites zone if the Outlook E-mail Security Update has been installed. Outlook Express 5.5 Service Pack 2 opens HTML e-mail messages in the Restricted sites zone if Microsoft Security Bulletin MS04-018 has been installed.
* By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode mitigates this vulnerability in the e-mail vector because reading e-mail messages in plain text is the default configuration for Outlook Express. See the FAQ section for this security update for more information about Internet Explorer Enhanced Security Configuration.
Workarounds for ActiveX Control Memory Corruption Vulnerability - CVE-2006-2383:
Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.
* Configure Internet Explorer to prompt before running ActiveX Controls or disable ActiveX Controls in the Internet and Local intranet security zone
You can help protect against this vulnerability by changing your Internet Explorer settings to prompt before running ActiveX controls. To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and then click Custom Level.
4. Under Settings, in the ActiveX controls and plug-ins section, under Run ActiveX controls and plug-ins, click Prompt or Disable, and then click OK.
5. Click Local intranet, and then click Custom Level.
6. Under Settings, in the ActiveX controls and plug-ins section, under Run ActiveX controls and plug-ins, click Prompt or Disable, and then click OK.
7. Click OK two times to return to Internet Explorer.
Impact of Workaround: There are side effects to prompting before running ActiveX controls. Many Web sites that are on the Internet or on an intranet use ActiveX to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX controls is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX controls. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone .
Add sites that you trust to the Internet Explorer Trusted sites zone.
After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.
To do this, follow these steps:
1. In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.
2. In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.
3. If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.
4. In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.
5. Repeat these steps for each site that you want to add to the zone.
6. Click OK two times to accept the changes and return to Internet Explorer.
Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and *.update.microsoft.com (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.
* Set Internet and Local intranet security zone settings to High to prompt before running ActiveX Controls and Active Scripting in these zones
You can help protect against this vulnerability by changing your settings for the Internet security zone to prompt before running ActiveX controls. You can do this by setting your browser security to High.
To raise the browsing security level in Microsoft Internet Explorer, follow these steps:
1. On the Internet Explorer Tools menu, click Internet Options.
2. In the Internet Options dialog box, click the Security tab, and then click the Internet icon.
3. Under Security level for this zone, move the slider to High. This sets the security level for all Web sites you visit to High.
Note If no slider is visible, click Default Level, and then move the slider to High.
Note Setting the level to High may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly even with the security setting set to High.
Impact of Workaround: There are side effects to prompting before running ActiveX controls. Many Web sites that are on the Internet or on an intranet use ActiveX to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX controls is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX controls. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone .
Add sites that you trust to the Internet Explorer Trusted sites zone.
After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.
To do this, follow these steps:
1. In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.
2. In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.
3. If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.
4. In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.
5. Repeat these steps for each site that you want to add to the zone.
6. Click OK two times to accept the changes and return to Internet Explorer.
Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and *.update.microsoft.com (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.
Prevent COM objects from running in Internet Explorer
You can disable attempts to instantiate a COM object in Internet Explorer by setting the kill bit for the control in the registry.
Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
For detailed steps that you can use to prevent a control from running in Internet Explorer, see Microsoft Knowledge Base Article 240797. Follow these steps in this article to create a Compatibility Flags value in the registry to prevent a COM object from being instantiated in Internet Explorer.
To set the kill bit for the DXImageTransform.Microsoft.Light ActiveX control, paste the following text in a text editor such as Notepad. Then, save the file by using the .reg file name extension.
You can apply this .reg file to individual systems by double-clicking it. You can also apply it across domains by using Group Policy. For more information about Group Policy, visit the following Microsoft Web sites:
Note You must restart Internet Explorer for your changes to take effect.
Impact of Workaround: The DXImageTransform.Microsoft.Light ActiveX control is a static filter used to create the effect of a light shining on the content of an object. This functionality would no longer be accessible for software using this ActiveX control.
FAQ for ActiveX Control Memory Corruption Vulnerability - CVE-2006-2383: What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could remotely take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.
What causes the vulnerability?
The DXImageTransform.Microsoft.Light ActiveX control could, if passed unexpected data, cause Internet Explorer to fail in a way that could allow code execution.
What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to exploit this vulnerability through Internet Explorer and then persuade a user to view the Web site. This can also include Web sites that accept user-provided content or advertisements, Web sites that host user-provided content or advertisements, and compromised Web sites. These Web sites could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to persuade users to visit the Web site, typically by getting them to click a link in an e-mail message or in an Instant Messenger request that takes users to the attacker's Web site. It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.
What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user is logged on and visits a Web site for any malicious action to occur. Therefore, any systems where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from this vulnerability.
What does the update do?
The update removes the vulnerability by modifying the way that Internet Explorer performs parameter validation.
When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.
When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.
COM Object Instantiation Memory Corruption Vulnerability - CVE-2006-1303:
A remote code execution vulnerability exists in the way Internet Explorer instantiates COM objects that are not intended to be instantiated in Internet Explorer. An attacker could exploit the vulnerability by constructing a specially crafted Web page that could potentially allow remote code execution if a user visited the specially crafted Web site. An attacker who successfully exploited this vulnerability could take complete control of an affected system.
Mitigating Factors for COM Object Instantiation Memory Corruption Vulnerability - CVE-2006-1303:
* Customers who have installed the security update included with Microsoft Security Bulletin MS05-052 or a later security bulletin for Internet Explorer are not at risk from attacks originating from the Internet zone.
* In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content or advertisements could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to persuade users to visit the Web site, typically by getting them to click a link in an e-mail message or instant messenger message that takes users to the attacker's Web site.
* An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
* The Restricted sites zone helps reduce attacks that could try to exploit this vulnerability by preventing ActiveX Controls from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, they could still be vulnerable to this issue through the Web-based attack scenario.
By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML e-mail messages in the Restricted sites zone. Additionally Outlook 2000 opens HTML e-mail messages in the Restricted sites zone if the Outlook E-mail Security Update has been installed. Outlook Express 5.5 Service Pack 2 opens HTML e-mail messages in the Restricted sites zone if Microsoft Security Bulletin MS04-018 has been installed.
* By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode mitigates this vulnerability. See the FAQ section for this security update for more information about Internet Explorer Enhanced Security Configuration.
Workarounds for COM Object Instantiation Memory Corruption Vulnerability - CVE-2006-1303:
Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.
Configure Internet Explorer to prompt before running ActiveX Controls or disable ActiveX Controls in the Internet and Local intranet security zone
You can help protect against this vulnerability by changing your Internet Explorer settings to prompt before running ActiveX controls. To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and then click Custom Level.
4. Under Settings, in the ActiveX controls and plug-ins section, under Run ActiveX controls and plug-ins, click Prompt or Disable, and then click OK.
5. Click Local intranet, and then click Custom Level.
6. Under Settings, in the ActiveX controls and plug-ins section, under Run ActiveX controls and plug-ins, click Prompt or Disable, and then click OK.
7. Click OK two times to return to Internet Explorer.
Impact of Workaround: There are side effects to prompting before running ActiveX controls. Many Web sites that are on the Internet or on an intranet use ActiveX to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX controls is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX controls. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone .
Add sites that you trust to the Internet Explorer Trusted sites zone.
After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.
To do this, follow these steps:
1. In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.
2. In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.
3. If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.
4. In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.
5. Repeat these steps for each site that you want to add to the zone.
6. Click OK two times to accept the changes and return to Internet Explorer.
Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and *.update.microsoft.com (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.
* Set Internet and Local intranet security zone settings to High to prompt before running ActiveX Controls and Active Scripting in these zones
You can help protect against this vulnerability by changing your settings for the Internet security zone to prompt before running ActiveX controls. You can do this by setting your browser security to High.
To raise the browsing security level in Microsoft Internet Explorer, follow these steps:
1. On the Internet Explorer Tools menu, click Internet Options.
2. In the Internet Options dialog box, click the Security tab, and then click the Internet icon.
3. Under Security level for this zone, move the slider to High. This sets the security level for all Web sites you visit to High.
Note If no slider is visible, click Default Level, and then move the slider to High.
Note Setting the level to High may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly even with the security setting set to High.
Impact of Workaround: There are side effects to prompting before running ActiveX controls. Many Web sites that are on the Internet or on an intranet use ActiveX to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX controls is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX controls. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone .
Add sites that you trust to the Internet Explorer Trusted sites zone.
After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.
To do this, follow these steps:
1. In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.
2. In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.
3. If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.
4. In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.
5. Repeat these steps for each site that you want to add to the zone.
6. Click OK two times to accept the changes and return to Internet Explorer.
Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and *.update.microsoft.com (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.
Prevent COM objects from running in Internet Explorer
You can disable attempts to instantiate a COM object in Internet Explorer by setting the kill bit for the control in the registry.
Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
For detailed steps that you can use to prevent a control from running in Internet Explorer, see Microsoft Knowledge Base Article 240797. Follow these steps in this article to create a Compatibility Flags value in the registry to prevent a COM object from being instantiated in Internet Explorer.
For example, to set the kill bit for a CLSID in the Wmm2fxa.dll file that is included in this security update, paste the following text in a text editor such as Notepad. Then, save the file by using the .reg file name extension.
You can apply this .reg file to individual systems by double-clicking it. You can also apply it across domains by using Group Policy. For more information about Group Policy, visit the following Microsoft Web sites:
Note You must restart Internet Explorer for your changes to take effect.
Impact of Workaround: There is no impact as long as the COM object is not intended to be used in Internet Explorer.
FAQ for COM Object Instantiation Memory Corruption Vulnerability - CVE-2006-1303: What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could remotely take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.
What causes the vulnerability?
When Internet Explorer tries to instantiate certain COM objects as ActiveX Controls, the COM objects may corrupt the system state in such a way that an attacker could execute arbitrary code.
What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to exploit this vulnerability through Internet Explorer and then persuade a user to view the Web site. This can also include Web sites that accept user-provided content or advertisements, Web sites that host user-provided content or advertisements, and compromised Web sites. These Web sites could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to persuade users to visit the Web site, typically by getting them to click a link in an e-mail message or in an Instant Messenger request that takes users to the attacker's Web site. It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.
What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user is logged on and visits a Web site for any malicious action to occur. Therefore, any systems where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from this vulnerability.
Note Customers who have installed the security update included with Microsoft Security Bulletin MS05-052 or a later security bulletin for Internet Explorer are not at risk from attacks originating from the Internet zone.
What does the update do?
Because not all COM objects are designed to be accessed through Internet Explorer, this update sets the kill bit for a list of Class Identifiers (CLSIDs) for COM objects that have been found to exhibit similar behavior to the COM object Instantiation Memory Corruption Vulnerability that is addressed in Microsoft Security Bulletin MS05-054. To help protect customers, this update prevents these CLSIDs from being instantiated in Internet Explorer. For more information about kill bits, see Microsoft Knowledge Base Article 240797.
The Class Identifiers and corresponding COM objects are as follows.
Class Identifier File
B4DC8DD9-2CC1-4081-9B2B-20D7030234EF Wmm2fxa.dll
C63344D8-70D3-4032-9B32-7A3CAD5091A5 Wmm2fxa.dll
353359C1-39E1-491b-9951-464FD8AB071C Wmm2fxa.dll
When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.
When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.
CSS Cross-Domain Information Disclosure Vulnerability - CVE-2005-4089:
An information disclosure vulnerability exists in Internet Explorer because it incorrectly interprets a specially crafted document as a cascading style sheet (CSS). An attacker could exploit the vulnerability by constructing a specially crafted Web page that could potentially lead to information disclosure if a user visited a specially crafted Web site or clicked a link in a specially crafted e-mail message. An attacker who successfully exploited this vulnerability could read file data from another Internet Explorer domain. However, user interaction is required to exploit this vulnerability.
Mitigating Factors for CSS Cross-Domain Information Disclosure Vulnerability - CVE-2005-4089:
* In a Web-based attack scenario, an attacker would have to host a Web site that contains a Web page that is used to exploit this vulnerability. An attacker would have no way to force users to visit a specially crafted Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's Web site.
* An attacker who successfully exploited this vulnerability could gain access to file data from a system other than that of the attacker s Web site.
* The Restricted sites zone helps reduce attacks that could try to exploit this vulnerability by preventing Active Scripting from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, they could still be vulnerable to this issue through the Web-based attack scenario.
By default, Outlook Express 6, Outlook 2002, and Outlook 2003 open HTML e-mail messages in the Restricted sites zone. Additionally Outlook 2000 opens HTML e-mail messages in the Restricted sites zone if the Outlook E-mail Security Update has been installed. Outlook Express 5.5 Service Pack 2 opens HTML e-mail messages in the Restricted sites zone if Microsoft Security Bulletin MS04-018 has been installed.
* By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode mitigates this vulnerability in the e-mail vector because reading e-mail messages in plain text is the default configuration for Outlook Express. See the FAQ section of this security update for more information about Internet Explorer Enhanced Security Configuration.
Workarounds for CSS Cross-Domain Information Disclosure Vulnerability - CVE-2005-4089:
Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.
* Configure Internet Explorer to prompt before running Active Scripting or disable Active Scripting in the Internet and Local intranet security zone
You can help protect against this vulnerability by changing your settings to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone. To do this, follow these steps:
1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and then click Custom Level.
4. Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.
5. Click Local intranet, and then click Custom Level.
6. Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.
7. Click OK two times to return to Internet Explorer.
Note Disabling Active Scripting in the Internet and Local intranet security zones may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly.
Impact of Workaround: There are side effects to prompting before running Active Scripting. Many Web sites that are on the Internet or on an intranet use Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use Active Scripting to provide menus, ordering forms, or even account statements. Prompting before running Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone .
Add sites that you trust to the Internet Explorer Trusted sites zone.
After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Int
