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Credit:
The information has been provided by Microsoft Security.
The original article can be found at: http://www.microsoft.com/technet/security/Bulletin/MS06-002.mspx
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Vulnerable Systems:
* Microsoft Windows 2000 Service Pack 4 Download the update
* Microsoft Windows XP Service Pack 1 and Microsoft Windows XP Service Pack 2 Download the update
* Microsoft Windows XP Professional x64 Edition Download the update
* Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service Pack 1 Download the update
* Microsoft Windows Server 2003 for Itanium-based Systems and Microsoft Windows Server 2003 with SP1 for Itanium-based Systems Download the update
* Microsoft Windows Server 2003 x64 Edition Download the update
* 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.
A remote code execution vulnerability exists in Windows because of the way that it handles malformed embedded Web fonts. An attacker could exploit the vulnerability by constructing a malicious embedded Web font that could potentially allow remote code execution if a user visited a malicious Web site or viewed a specially crafted e-mail message. An attacker who successfully exploited this vulnerability could take complete control of an affected system.
Mitigating Factors for Windows Embedded Web Font Vulnerability - CVE-2006-0010:
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. Also, Web sites that accept or host user-provided content or advertisements, and compromised Web sites, may contain malicious 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 or Instant Messenger request 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 where the e-mail vector is concerned although clicking on a link would still put users at risk. In Windows Server 2003, Microsoft Outlook Express uses plain text for reading and sending messages by default. When replying to an e-mail message that is sent in another format, the response is formatted in plain text. See the FAQ section of this vulnerability for more information about Internet Explorer Enhanced Security Configuration.
Workarounds for Windows Embedded Web Font Vulnerability - CVE-2006-0010:
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.
* 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.
For information about this setting in Outlook Express 6, see Microsoft Knowledge Base Article 291387.
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.
* Configure Font Download to Prompt or Disable in the Internet and Local Intranet Zones.
Impact of Workaround: Web sites that depend on embedded fonts may fail to render.
1. From within Internet Explorer, Click on the Tools menu then click Internet Options.
2. Click on the Security Tab.
3. To change the setting for the Internet zone select Internet and press the Custom Level button.
4. Scroll down to the Downloads section and select Prompt or Disable for the Font Download security setting.
5. Press OK to close the Security Settings dialog box.
6. Press OK to close the Internet Options dialog box.
FAQ for Windows Embedded Web Font Vulnerability - CVE-2006-0010:
What is the scope of the vulnerability?
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 Windows displays a specially formed embedded Web font, 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 take complete control of the affected system.
How could an attacker exploit the vulnerability?
An attacker could exploit this vulnerability by creating a malicious Web page or an HTML e-mail message and then persuading the user to visit the page or to view the HTML e-mail message. If the user visited the page or viewed the e-mail message, the attacker could access information from other Web sites, could access local files in predetermined locations on the system, or could cause malicious code to run in the security context of the locally logged on user. An attacker could also try to compromise a Web site and have it display malicious content. Additionally, 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 e-mail or visiting Web sites for any malicious action to occur. Therefore, any systems where e-mail is read or where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from this vulnerability. Systems that are not typically used to read e-mail or to visit Web sites, such as most server systems, are at a reduced risk.
I am running Internet Explorer on 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. This mode mitigates this vulnerability where the e-mail vector is concerned although clicking on a link would still put users at risk. In Windows Server 2003, Microsoft Outlook Express uses plain text for reading and sending messages by default. When replying to an e-mail message that is sent in another format, the response is formatted in plain text.
What is Internet Explorer Enhanced Security Configuration?
Internet Explorer Enhanced Security Configuration is a group of preconfigured Internet Explorer settings that reduce the likelihood of a user or of an administrator downloading and running malicious Web content on a server. Internet Explorer Enhanced Security Configuration reduces this risk by modifying many security-related settings. This includes the settings on the Security tab and the Advanced tab in the Internet Options dialog box. Some of the important modifications include the following:
* Security level for the Internet zone is set to High. This setting disables scripts, ActiveX controls, Microsoft Java Virtual Machine (MSJVM), and file downloads.
* Automatic detection of intranet sites is disabled. This setting assigns all intranet Web sites and all Universal Naming Convention (UNC) paths that are not explicitly listed in the Local intranet zone to the Internet zone.
* Install On Demand and non-Microsoft browser extensions are disabled. This setting prevents Web pages from automatically installing components and prevents non-Microsoft extensions from running.
* Multimedia content is disabled. This setting prevents music, animations, and video clips from running.
What does the update do?
The update removes the vulnerability by modifying the way that Windows validates the length of a message before it passes the message to the allocated buffer when handling embedded Web fonts.
When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.
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