These important security updates should be applied promptly:

Microsoft Security Release – November 2011
http://technet.microsoft.com/en-us/security/bulletin/ms11-nov
http://blogs.technet.com/b/srd/archive/2011/11/08/assessing-the-exploitability-of-ms11-083.aspx

ICS Analysis
http://isc.sans.edu/diary.html?storyid=11971

QUOTE: The vulnerability presents itself in the specific scenario where an attacker can send a large number of specially crafted UDP packets to a random port that does not have a service listening. While processing these network packets it is observed that some used structures are referenced but not dereferenced properly. This unbalanced reference counting could eventually lead to an integer overflow of the reference counter