According to Gil Dabah, a researcher from Tel Aviv who goes by the nickname "arkon," the Windows' kernel harbors a heap overflow vulnerability. Dabah also posted a short proof-of-concept to demonstrate the bug on RageStorm.com, a site he and two others run.

"Microsoft is investigating reports of a possible vulnerability in Windows Kernel," said Jerry Bryant on Friday. "Upon completion of the investigation, Microsoft will take appropriate actions to protect customers."

In an , Danish bug tracker Secunia pinpointed the bug in the "Win32k.sys" kernel-mode device driver, the kernel component of the Windows subsystem. Attackers could exploit the flaw using "GetClipboardData," an API (application programming interface) that retrieves data from the Window clipboard.

A successful exploit would allow hackers to execute their attack code in kernel mode, which would then let them infect the PC with malware or pillage any data on the machine.

The flaw exists in several versions of Windows, including XP SP3, Server 2003 R2, Vista, and Windows Server 2008 SP2, said Secunia, which rated the bug as "less critical," the firm's second-lowest threat ranking.