Microsoft has released Microsoft Security Advisory 2639658 to address a vulnerability in the Win32k TrueType font parsing engine. By convincing a user to open a malicious email attachment, an attacker may be able to exploit this vulnerability and execute arbitrary code.
Microsoft has indicated that it is aware of targeted attacks exploiting this vulnerability. The Duqu malware may exploit this vulnerability.
UPDATE: Microsoft has provided an update to address this vulnerability in Microsoft Security Bulletin MS11-087.
US-CERT encourages users and administrators to take the following actions to help mitigate the risks of this vulnerability and the Duqu malware: