Additional technical information is available regarding the Microsoft Windows Embedded OpenType font heap overflow vulnerability.
Microsoft Windows contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code.
This vulnerability exists due to insufficient boundary restrictions by the Embedded OpenType Font Engine. An unauthenticated, remote attacker could exploit this vulnerability by convincing a user to view a malicious website. If the user views the site, the attacker could execute arbitrary code with the privileges of the user.
Microsoft has confirmed this vulnerability in a security bulletin and released updated software.
The following Microsoft products are affected:
Windows 2000 SP4 and prior
Windows XP SP3 and prior
Windows XP Professional x64 Edition SP2 and prior
Windows Server 2003 SP2 and prior
Windows Server 2003 x64 Edition SP2 and prior
Windows Server 2003 for Itanium-based Systems SP2 and prior
Windows Vista SP2 and prior
Windows Vista x64 Edition SP2 and prior
Windows Server 2008 for 32-bit Systems SP2 and prior
Windows Server 2008 for x64-based Systems SP2 and prior
Windows Server 2008 for Itanium-based Systems SP2 and prior
Attackers cannot directly exploit this vulnerability and instead rely upon user participation. Attackers may embed malicious content within public websites or attempt to convince users to visit malicious sites by sending links in e-mail messages. An attacker may rely upon social engineering techniques to convince users to participate in an exploit.
Systems most at risk are end-user systems on which users run applications with elevated privileges. If the user holds elevated privileges, an exploit could result in a complete system compromise. Systems that restrict user privileges or those with built-in privilege separation could be impacted less as the result of an exploit because any executed code would run with limited privileges.
The Cisco Applied Intelligence team has created an Applied Mitigation Bulletin to address vulnerabilities that Microsoft disclosed in the July 2009 security bulletin release. This Cisco bulletin, which assists administrators in identifying or mitigating these vulnerabilities using Cisco devices, is available at the following link: Cisco Applied Mitigation Bulletin: Microsoft Security Bulletin for July 2009
The update available from Microsoft corrects this vulnerability by improving font parsing.
Microsoft has released a security bulletin at the following link: MS09-029
An unauthenticated, remote attacker could exploit this vulnerability to execute arbitrary code with the privileges of the user. If that user holds Administrator privileges, the attacker could completely compromise the vulnerable system.
This vulnerability exists due to insufficient boundary restrictions by the Embedded OpenType Font Engine. Specifically, the vulnerability exists in the t2embed.dll library due to an integer truncation error. The affected component fails to properly limit the size of input within name tables when processing malformed embedded fonts. The processing of an overly large parameter could trigger a heap-based buffer overflow, possibly corrupting memory.
An unauthenticated, remote attacker could exploit this vulnerability by convincing a user to view a website that contains a malicious embedded font. The processing of the website could trigger memory corruption that the attacker could leverage to execute arbitrary code with the privileges of the user.
Administrators are advised to apply the available software updates.
Administrators may consider disabling embedded fonts in Internet Explorer.
Administrators may consider unregistering or preventing access to the t2embed.dll component.
Users are advised not to visit websites or follow links that have suspicious characteristics or cannot be verified as safe.
Users are advised to run applications with the least necessary privileges.
Microsoft customers can obtain updates directly by using the links in the security bulletin. These updates are also distributed by Windows automatic update features and available on the Windows Update website. Microsoft Windows Server Update Services (WSUS), Systems Management Server, and System Center Configuration Manager can assist administrators in deploying software updates.
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