Last Updated: 2007-06-03 11:07:48 UTC ~ "...The exploit was discovered on December 15, 2006, and made public since the end of May 2007. The design of IIS 5.x allows to bypass basic authentication by using the hit highlight feature. Microsoft's response seems to be a bit atypical for them as it includes a section on how to reproduce the exploit. In other words: Microsoft is telling the world how to exploit their products being used by their customers. Not that the worst of those interested in it did not already know, but the one thing we need from Microsoft is not the exploit, but the patch or at least a decent work-around. And that patch is lacking. Their only defensive advice is to upgrade to IIS 6.0. Since this means that you would also need to upgrade the windows 2000 or XP to Windows 2003, and that such an upgrade isn't free, nor easy. So what do we do when Microsoft does not give any advice but to upgrade to IIS 6.0 ? Let's look at alternatives. Feel free to write in if you know more effective alternatives:
* Most probably there is a way to remove something or change some registry setting to prevent this, unfortunately exactly what is neither documented nor validated.
* Try to use application level firewalls (filters), while they aren't the easiest to configure considering all the ways URLs can be encoded, it's something that might help for a while, but getting it fully right will be a pain. If you have the infrastructure it can be a temporary measure till you can upgrade IIS, solving the actual problem.
* Upgrade to apache or another web server, with or without a (cross) upgrade of the OS.
* Scramble an upgrade to Windows 2003, potentially on more potent hardware...
Last Review: April 23, 2007
"...We strongly recommend that all users upgrade to Microsoft Internet Information Services (IIS) version 6.0 running on Microsoft Windows Server 2003..."
CVSS Severity: 10.0 (High)
Range: Remotely exploitable
MS IIS 5.x exploit released
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