DoS bug bites Microsoft's first security product

It was only a question of time

A flaw with Microsoft's first security product leaves it vulnerable to denial of service attacks.

The problem arises because Microsoft's Internet Security and Acceleration (ISA) Server's Web Proxy service doesn't handle particular requests if they exceed a certain length, causing the program to crash if its Web Publishing features are enabled.

In a security notice, Microsoft admitted: "Processing such a [malformed] request would result in an access violation, which would cause the Web Proxy service to fail. This would disrupt all ingoing and outgoing Web proxy requests until the service was restarted."

Although this means that a hacker might be able to mount a denial of service attack, it would not allow an attacker to take control of the firewall or access the systems it is meant to protect.

Still, the flaw is embarrassing for Microsoft, which has heavily promoted ISA Server as an enterprise firewall and Web cache, and now finds itself (ironically) dealing with a security problem with its own security product.

Microsoft has made a patch available to address the vulnerability and advised administrators using Web Publishing to apply it immediately. The fix will also be included in the first service pack of ISA Server.

Web Publishing allows external users to access internal Web sites without exposing the actual address of the sites, and is likely to be widely used. This bug was discovered by security researchers at FSC Internet and SecureXpert Labs. ®

Related Link

Microsoft's security bulletin

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