Info on this can be found at New Windows 0-day vulnerability emerges, bypasses UAC | WinRumors
"Giuliani warned that Windows XP, Vista and Windows 7 were all vulnerable to attack, including 32-bit and 64-bit editions. Prevx says they have not see any malware exploiting this flaw but warned “we expect to see this exploit being actively used by malware very soon – it’s an opportunity that malware writers surely won’t miss.”
The vulnerability is located in Win32ksys’s NtGdiEnableEUDC API according to Prevx. The API is not correctly validating some inputs resulting in a stack overflow. A malicious attacker could redirect the overwritten return address to their malicious code and execute it with kernel mode privileges. As the flaw is a privilege escalation exploit, it bypasses the User Account Control (UAC) and Limited User Account technologies implemented in Windows Vista and Windows 7."
Soon be time to batten down the hatches again...