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Thursday, February 18, 2010

Windows plagued by 17-year old escalation bug

Back in June of last year, a vulnerability was discovered in the Windows Kernel which that allows untrusted users to take complete control of systems running most versions of Microsoft Windows.

The vulnerability resides in a feature known as the Virtual DOS Machine, which Microsoft introduced in 1993 with Windows NT, according to this writeup penned by Tavis Ormandy of Google. Using code written for the VDM, an unprivileged user can inject code of his choosing directly into the system's kernel, making it possible to make changes to highly sensitive parts of the operating system.

"You can in theory write to memory segments that are otherwise considered highly trusted and sensitive," said Tom Parker, a director in the security consulting services group at Securicon, a Washington, DC-based security practice. "So for example, malware could possibly use it to install a key logger."

The vulnerability exists in all 32-bit versions of Microsoft OSes released since 1993, and proof-of-concept code works on the XP, Server 2003, Vista, Server 2008, and 7 versions of Windows, Ormandy reported.

Ormandy said the security hole can easily be closed by turning off the MSDOS and WOWEXEC subsystems. The changes generally don't interfere with most tasks since they disable rarely-used 16-bit applications. He said he informed Microsoft security employees of the vulnerability in June.

"Regrettably, no official patch is currently available (then late January 2010)," he wrote. "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."

Microsoft security officials - who are already working double-duty responding to a potent Internet Explorer bug used to attack Google - said they are looking in to Ormandy's advisory and are not aware of attacks that target the reported vulnerability.

Early this month, Microsoft did finally put out a security update patch to this bug, more than 6 month after it was reported. Laughably in standard Microsoft quality and style, this update promptly crippled some systems with the notorious Blue Screen of Death. The systems thus falls into a reboot loop. The only way to solve the reboot looping or BSOD is by removing the patch... or such was the conclusion of thread pertaining to the issue on the MS support forums.

And people wonder why I still claim Windows isn't a very secure OS.

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