Tavis Ormandy has discovered a vulnerability in Microsoft Windows, which can be exploited by malicious, local users to cause a Denial of Service (DoS).

The vulnerability is caused due to a logic error in the "GreStretchBltInternal()" function in win32k.sys when the same hdcDest and hdcSrc Device Context (DC) handles are passed as arguments to the "BitBlt()" API. This can be exploited to unmap the same object twice, triggering an unhandled exception in the kernel that crashes the system.

The vulnerability is confirmed in a fully patched version of Windows 7 Professional. No other supported versions of Windows currently seem affected.

Solution
Grant access to trusted users only.

Provided and/or discovered by
Tavis Ormandy

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