One day after a Google security researcher released code to expose a flaw that affects every release of the Windows NT kernel -- from Windows NT 3.1 (1993) up to and including Windows 7 (2009) -- Microsoft dropped a security advisory to acknowledge the issue and warn of the risk of privilege escalation attacks.
Microsoft warns that a malicious hacker could exploit this vulnerability to run arbitrary code in kernel mode. For an attack to be successful, the attacker must have valid logon credentials.
The flaw does not affect Windows operating systems for x64-based and Itanium-based computers, Microsoft said.
According to Tavis Ormandy, the Google researcher who released the flaw details, Microsoft was notified about the issue in June 2009. After waiting several months and not seeing a patch, he decided it was in the best interest of everyone to go public.
As an effective and easy to deploy workaround is available, I have concluded that it is in the best interest of users to go ahead with the publication of this document without an official patch. It should be noted that very few users rely on NT security, the primary audience of this advisory is expected to be domain administrators and security professionals.
Ormandy's advisory includes instructions for temporarily disabling the MSDOS and WOWEXEC subsystems to prevent an attack from functioning. This can be done via Group Policy.
The mitigation in Microsoft's advisory mirrors the advice from Ormandy.