12/28/2009

Microsoft IIS vuln leaves users open to remote attack

Filed under: — By Aviran Mordo @ 12:23 pm

A researcher has identified a vulnerability in the most recent version of Microsoft’s Internet Information Services that allows attackers to execute malicious code on machines running the popular webserver.

The bug stems from the way IIS parses file names with colons or semicolons in them, according to researcher Soroush Dalili. Many web applications are configured to reject uploads that contain executable files, such as active server pages, which often carry the extension “.asp.” By appending “;.jpg” or other benign file extensions to a malicious file, attackers can bypass such filters and potentially trick a server into running the malware.

There appears to be some disagreement over the severity of the bug, which Dalili said affects all versions of IIS. While he rated it “highly critical,” vulnerability tracker Secunia classified it as “less critical,” which is only the second notch on its five-tier severity rating scale.

 

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