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Microsoft faces another security nightmare

A new zero day bug

Software giant Microsoft is facing a bit of an insecurity crisis after a serious of zero day exploits have hit its successful Windows 7 Operating system.

First there was the Aurora exploit in the first of the year, then there was the Stuxnet case. Yesterday another serious 0-day flaw has been shown on a Chinese bulletin board. According to Security outfit Prevx, the flaw resides in win32k.sys, which is the kernel mode part of the Windows subsystem. It allows even limited user accounts to execute arbitrary code in kernel mode. What appears to be causing it Win32k.sys's NtGdiEnableEUDC API is not rightly validating some inputs.

This creates a stack overflow and overwriting the return address stored on the stack. This means that a malicious attacker can redirect the overwritten return address to his malicious code and execute it. Since it has kernel mode privileges it has practically total control of the system. Windows 7's defences, such as User Account Control and Limited User Account technology are vulnerable. So far it has not been seen in the wild.

But now that it has been published online it is only a matter of time before malware is using it.

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