A security flaw in Server Message Block 2 - the Microsoft network file and print-sharing protocol that is integral to various versions of Windows - was originally thought to only crash affected PCs, causing a 'blue screen of death' crash.
However, last week saw Florida-based Immunity, the developer of the Canvas penetration testing framework, creating a working remote code exploit, details of which were released to subscribers of its early updates programme.
Last Friday, meanwhile, Microsoft confirmed that its research labs had verified the flaw exploited on a test basis by Immunity and was working on a fix.
"We have analysed the code ourselves and can confirm that it works reliably against 32-bit Windows Vista and Windows Server 2008 systems", said the Microsoft Security Response Center engineering team in a company blog.
"The exploit gains complete control of the targeted system and can be launched by an unauthenticated user."
Until a security patch for the problem has been developed, Microsoft is recommending that users download and run the an automated `fix-it' utility made available over the weekend on its support site.
In use, the utility disables the SMB 2 service, but the bad news, Infosecurity notes, is that it no longer longer possible for the host PC to communicate to file servers and network printers using the protocol.
Read Microsoft Chief Security Advisor, Roger Halbheer's blog, on Infosecurity.