Story found via Neowin, via Winrumors, original at Prevx. It being the Thanksgiving Holiday here in the states I assume most of the MS staff here is off and the only official statement I can find from Microsoft at the moment is from a German Microsoft TechNet blog post. Microsoft is investigating new vulnerability in Windows Kernel (translated).
Being a privilege escalation exploit, it bypasses by design even the protection given by the User Account Control and Limited User Account technology implemented in Windows Vista and Windows 7. All Windows XP/Vista/7 both 32 and 64 bit are vulnerable to this attack.