Microsoft warns of new server vulnerability

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A new, unpatched vulnerability exists in one of Microsoft's server products, the company warned late on Monday.

In a technical bulletin, the company said it is looking into "public reports of a possible vulnerability in Microsoft Internet Information Services (IIS)".

The company said that a flaw exists in a certain type of web-serving operation.

"An elevation of privilege vulnerability exists in the way that the WebDAV extension for IIS handles HTTP requests," Microsoft said. "An attacker could exploit this vulnerability by creating a specially crafted anonymous HTTP request to gain access to a location that typically requires authentication."

Microsoft said it is not aware of attacks using the vulnerability. The company said it may provide an update as part of its monthly Patch Tuesday or, depending on the severity, could provide a fix outside its monthly patching schedule.

In the meantime, the company listed on its website certain configuration settings that can help mitigate the impact of the flaw.

Talkback

At first glance, the issue with IIS 6 seems like little more than a possible problem for those with sensitive materials reserved for viewing by only authorised individuals. However, for those who are serious about security, this is perhaps a non issue given that public and sensitive materials are not typically kept on the same server as it lacks the ability to construct sufficient isolation between zones of trust.

The larger potential problem with the IIS 6 issue is that it has the potential for malicious remote hackers to view and upload files to the server by taking advantage of a bug in the way that Microsoft software’s processes Unicode tokens do. Hence, it would conceivably be a trivial matter to replace trusted files on the Web server with malicious files. One example of such a potential risk would be to replace trusted PDF files containing company’s customer data with malicious PDF files that take advantage of recently patched Adobe PDF issues.

There are numerous examples of the use of obfuscation in malicious PDF files hosted on Chinese Web servers that have successfully been able to avoid detection by numerous anti-virus vendor products. The ability to upload an obfuscated PDF file onto a popular website has the potential of wreaking havoc for unsuspecting users as it has a high likelihood of not being detected by traditional technologies such as AV.

Potential risks around IIS 6 server again remind us that the implied trust even for popular websites is perhaps questionable in the current environment. In the protection of our user communities, traditional defenses such as signature-based AV have proven to be futile. The most effective risk mitigation is to eliminate the possibility that unauthorised software is permitted to operate or execute within your environment using current technologies such as whitelisting application control. In preventing unauthorised software from operating, you are effectively mitigating the ability of files such as a PDF file that contains malicious Javascript from downloading and executing malware within your environment.

lumension 20 May, 2009 01:54
Reply

Maybe a change to an xxIX server would be a wise solution, plus you would have a lot of extra benefits, like speed, uptime, consumer confidence, etc.

ator1940 20 May, 2009 11:50
Reply

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