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Credit:
The information has been provided by Microsoft Product Security.
The original article can be found at: http://www.microsoft.com/technet/security/Bulletin/MS08-023.mspx
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Affected Software:
Operating System - Component - Maximum Security Impact - Aggregated Severity Rating - Bulletins Replaced by This Update
* Microsoft Windows 2000 Service Pack 4 - Microsoft Internet Explorer 5.01 Service Pack 4 - Remote Code Execution - Critical - None
* Microsoft Windows 2000 Service Pack 4 - Microsoft Internet Explorer 6 Service Pack 1 - Remote Code Execution - Critical - None
* Windows XP Service Pack 2 - - Remote Code Execution - Critical - None
* Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2 - - Remote Code Execution - Critical - None
* Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2 - - Remote Code Execution - Moderate - None
* Windows Server 2003 x64 Edition and Windows Server 2003 x64 Edition Service Pack 2 - - Remote Code Execution - Moderate - None
* Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium-based Systems - - Remote Code Execution - Moderate - None
* Windows Vista and Windows Vista Service Pack 1 - - Remote Code Execution - Important - None
* Windows Vista x64 Edition and Windows Vista x64 Edition Service Pack 1 - - Remote Code Execution - Important - None
* Windows Server 2008 for 32-bit Systems - - Remote Code Execution - Low - None
* Windows Server 2008 for x64-based Systems - - Remote Code Execution - Low - None
* Windows Server 2008 for Itanium-based Systems - - Remote Code Execution - Low - None
ActiveX Object Memory Corruption Vulnerability - CVE-2008-1086
A remote code execution vulnerability exists in the ActiveX control hxvz.dll. An attacker could exploit the vulnerability by constructing a specially crafted Web page. When a user views the Web page, the vulnerability could allow remote code execution. An attacker who successfully exploited this vulnerability could gain the same user rights as the logged on user
CVE Information:
CVE-2008-1086
Mitigating Factors for ActiveX Object Memory Corruption Vulnerability - CVE-2008-1086
Mitigation refers to a setting, common configuration, or general best-practice, existing in a default state, that could reduce the severity of exploitation of a vulnerability. The following mitigating factors may be helpful in your situation:
* 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 could contain specially crafted content that could exploit this vulnerability. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail 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 and Windows Server 2008 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone. See the FAQ subsection of this vulnerability section for more information about Internet Explorer Enhanced Security Configuration.
* By default, this ActiveX control is not included in the default allow-list for ActiveX controls in Internet Explorer 7. Only customers who have explicitly approved this control by using the ActiveX opt-in feature are at risk to attempts to exploit this vulnerability. However, if a customer has used this ActiveX control in a previous version of Internet Explorer, then this ActiveX control is enabled to work in Internet Explorer 7, even if the customer has not explicitly approved it using the ActiveX opt-in feature.
Workarounds for ActiveX Object Memory Corruption Vulnerability - CVE-2008-1086
Workaround refers to a setting or configuration change that does not correct the underlying vulnerability but would help block known attack vectors before you apply the update. Microsoft has tested the following workarounds and states in the discussion whether a workaround reduces functionality:
* 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.
Note The Class Identifiers and corresponding files where the ActiveX objects are contained are documented under What does the update do? in the FAQ for ActiveX Object Memory Corruption Vulnerability - CVE-2008-1086 section. Replace {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} below with the Class Identifiers found in this section.
To set the kill bit for a CLSID with a value of {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}, paste the following text in a text editor such as Notepad. Then, save the file by using the .reg file name extension.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{ XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX }]
"Compatibility Flags"=dword:00000400
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:
* Group Policy collection
* What is Group Policy Object Editor?
* Core Group Policy tools and settings
Note You must restart Internet Explorer for your changes to take effect.
* Impact of Workaround: There is no impact as long as the object is not intended to be used in Internet Explorer.
FAQ for ActiveX Object Memory Corruption Vulnerability - CVE-2008-1086
What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could gain the same user rights as the logged on user.
If a user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could 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. 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.
What causes the vulnerability?
When the ActiveX control is used in Internet Explorer, the control 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 convince a user to view the Web site. This can also include compromised Web sites and Web sites that accept or host user-provided content or advertisements. 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 convince 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.
I am running Internet Explorer for Windows Server 2003. Does this mitigate this vulnerability?
Yes. By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted Web content on a server. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone. See also Managing Internet Explorer Enhanced Security Configuration.
What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user be logged on and visit 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?
This update sets the kill bit for a list of Class Identifiers (CLSIDs).
The Class Identifiers and corresponding files are as follows:
Class Identifier - File
{314111b8-a502-11d2-bbca-00c04f8ec294} - hxvz.dll
{314111c6-a502-11d2-bbca-00c04f8ec294} - hxvz.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.
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