win32k.sys in the kernel in Microsoft Windows 2000 SP4, XP SP2 and SP3, Server 2003 SP2, Vista Gold, SP1, and SP2, and Server 2008 Gold and SP2 does not correctly validate an argument to an unspecified system call, which allows local users to gain privileges via a crafted application that triggers a NULL pointer dereference, aka "Win32k NULL Pointer Dereferencing Vulnerability."