Back on November 11th, 2009 we confirmed Laurent Gaffié’s remote exploit for Windows that causes a kernel crash. The operating system actually freezes creating a denial of service when for example a user is tricked into clicking on a link to a malicious SMB share on a web page. The SMB client goes into an infinite loop when processing this malformed request according to Microsoft. The video below demonstrates this effect, having a user click a web site link and showing the crash.
Following the Juniper kernel flaw posts, we received a number of inquiries regarding how to determine the option value to use, however we were somewhat reluctant to provide that level of detail. Now that exploit code has been published elsewhere, there is little reason not to answer this question.
We have noted some interesting responses since our post yesterday detailing the information in Juniper bulletin PSN-2010-01-623 and our thoughts on its somewhat understated effect. Since our post yesterday, the bulletin has been updated, becoming more specific about the versions affected (basically excluding JUNOS version 10.x and versions no longer supported by Juniper). We have tested all 256 permutations of the Options field in the TCP header, and reproduced the kernel crash, which is demonstrated in the video below.