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Last night I attended the Microsoft Security Response Team webcast regarding the Out Of Band patch for the ASP.net padding Oracle vulnerability discovered by Juliana Rizzo and Thai Duong 11 days before.

My main objective in watching the webcast (which is not my usual habit) was to find out if systems that have the described workaround applied still need to apply the patch. The webcast did not give a definitive answer but this YouTube video and the Netifera website and the twitter accounts Thai Duong provide the answer: Yes you should apply the patch a.s.a.p!

However the Q&A section of the talk did give me, as a security operations guy, quite some food for thought. I made some notes in my own Twitter feed, which I have summarized here.

Q: Why did Microsoft release and OOB update for a vulnerability rated “only” as important?
A: The vulnerability itself is rated as Important because it is not a vulnerability that directly leads to remote code execution on the vulnerable system, however exploitation of the vulnerability will lead to disclosure of all information in the webroot including web.config. This information can be used for session hijacking, compromising backend databases and to attack associations between websites, e.g. the association of a website with PayPal. Hence an out of band patch was warranted.

Q: Why only release to the download center and not to WSUS etc?
A: We felt we needed to get this update out quickly, the people that need to apply this patch quickly are mainly enterprises who are capable of applying patches without the aid of WSUS. Developing the WSUS capabilities would add another few days of delay to the deployment of this patch.

Q: Is the attack actively used?

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By Yaniv Miron

lolcat adaptation #3, a Creative Commons Attribution No-Derivative-Works (2.0) image from kevinsteele's photostream

Exploit wednessday ois the day after patch Tuesday, the second Tuesday of the month when Microsoft releases its patches. While some people say it’s impossible to write an attack in one day, Yaniv has seen it happen and tries to explain how.

This process is based on diffing. Diffing means finding the differences between the old and the patched version of the binary file.

This could be done on the same machine, or between two different versions of the OS (e.g. Windows XP and Vista).

The toolkit for a typical patch analysis consists of:

• Diff programs
• Compare programs
• Decompiles  and compilers
• Different versions of windows

Yaniv, then went off to demonstrate a to us the creation of an exploit for MS10-005.

First of all information from public source was gathered to find out which program was effected, what the root cause of the vulnerability was and in which version of Windows the problem is present.

The next part is extracting the patch and analyzing it. First this that needs to be done is finding the files that will be updated. The these files will be compared against the original file, just to find which functions have been changed.

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Overview of Microsoft patches due today by Microsoft

Microsoft is even more vague than usual about the patches it plans to release today.

In this patch announcement Microsoft only states that it plans to release 5 patches.

This is the data currently known:

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