An unchecked buffer in a Windows component could cause web server compromise, Microsoft warns today.

According to Microsoft, the flaw affects Windows 2000 only (i.e. not XP or NT). It revolves around Microsoft's flawed implementation of the World Wide Web Distributed Authoring and Versioning (WebDAV) protocol in IIS. WebDAV is a set of extensions to the Hyper Text Transfer Protocol (HTTP) which provides a standard for editing and file management between computers on the Internet.

On vulnerable Windows 2000 boxes running IIS, the vulnerability can have dire consequences.

"An attacker could exploit the vulnerability by sending a specially formed HTTP request to a machine running Internet Information Server (IIS)," Microsoft's advisory warns. "The request could cause the server to fail or to execute code of the attacker's choice. The code would run in the security context of the IIS service (which, by default, runs in the LocalSystem context)."

Microsoft describes the vulnerability as critical and has released a patch along with advice on workarounds for customers who are not immediately able to apply the fix.

The vulnerability is reminiscent of the flaw which was infamously exploited by the Code Red and Nimda worms.

Microsoft is clearly taking the problem seriously.

Stuart Okin, chief security officer of Microsoft UK, phoned us gives us a heads up on the patch - a first, in our experience. We understand he has spent the day notifying Microsoft's largest UK customers of the problem.

Security tools firm ISS has published an advisory which explains the vulnerability more clearly than the Redmond advisory. According to ISS, versions of IIS 5.0 on Windows 2000 up to and including Service Pack 3 are vulnerable to the flaw. ®

External Links

Microsoft's advisory
ISS alert