Windows 7 64 bit Memory Corruption Vulnerability has been discovered in Microsoft Windows. The vulnerability is caused due to an error in win32k.sys and can be exploited to corrupt memory via e.g. a specially crafted web page containing an IFRAME with an overly large “height” attribute viewed using the Apple Safari browser. This could evolve either into a local privilege escalation issue or a remote code execution as admin problem. In particular if triggered by more popular browsers (Internet Explorer, Firefox, Chrome).
Source: https://thehackernews.com/2011/12/windows-7-64-bit-memory-corruption.html