Microsoft IIS Zero-Day Vulnerability Reported

Exploit code affecting the FTP module for certain versions of Microsoft IIS has been posted online. US-CERT recommends taking countermeasures.

Thomas Claburn, Editor at Large, Enterprise Mobility

August 31, 2009

2 Min Read

Proof-of-concept code for a zero-day vulnerability that affects the FTP module of Microsoft IIS 5.0 and 6.0 has been posted online, prompting a warning from US-CERT.

"US-CERT is aware of a public report of a vulnerability affecting the Microsoft Internet Information Services (IIS) FTP service," US-CERT said on Monday. "This vulnerability may allow a remote attacker to execute arbitrary code."

The cybersecurity agency is advising IT administrators to disable anonymous write access to IIS FTP servers as a means of risk mitigation.

The risk posed by this vulnerability remains unclear. Symantec researchers didn't have an immediate comment as they were still in the process of analyzing the vulnerability exploited by the proof-of-concept code.

Microsoft also said that it was still looking into the reported vulnerability. "Microsoft is investigating new public claims of a possible vulnerability in IIS 5 and IIS 6 File Transfer Protocol (FTP) and are currently unaware of any attacks trying to use the claimed vulnerability or of customer impact," a company spokesperson said in an e-mailed statement.

Microsoft said that it will take steps to determine how customers can protect themselves if the vulnerability is confirmed. The company said it will take whatever action is appropriate to protect customers once the investigation is complete.

Emerging Threats, an open-source threat signature project that receives funding from the Army Research Office and the National Science Foundation, has posted a signature for the proof-of-concept code.

Microsoft typically releases its Security Bulletins on the second Tuesday of every month. This coming Thursday, the company should release preliminary information about the Security Bulletins that it expects to release on Tuesday, September 8th.

It remains to be seen whether Microsoft will have enough time to address this vulnerability in its September patch cycle.

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About the Author(s)

Thomas Claburn

Editor at Large, Enterprise Mobility

Thomas Claburn has been writing about business and technology since 1996, for publications such as New Architect, PC Computing, InformationWeek, Salon, Wired, and Ziff Davis Smart Business. Before that, he worked in film and television, having earned a not particularly useful master's degree in film production. He wrote the original treatment for 3DO's Killing Time, a short story that appeared in On Spec, and the screenplay for an independent film called The Hanged Man, which he would later direct. He's the author of a science fiction novel, Reflecting Fires, and a sadly neglected blog, Lot 49. His iPhone game, Blocfall, is available through the iTunes App Store. His wife is a talented jazz singer; he does not sing, which is for the best.

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