Microsoft issued a formal security advisory late Tuesday on a reported zero-day flaw in Windows Vista and Windows Server 2008. However, the software maker also said that the flaw does not affect the final version of Windows 7, contrary to earlier reports.

"Microsoft is investigating new public reports of a possible vulnerability in Microsoft Server Message Block (SMB) implementation," Microsoft said in the advisory. "We are not aware of attacks that try to use the reported vulnerabilities o...