See Black Hat 2006 Skype Analysis.

The description of the flaw is on page 104 of the PDF, labelled as 89/98 in the slides. It is a heap overflow that allows remote execution of code, with one single source-unidentified UDP packet. The sildes also give the exact UDP packet that needs to be sent. See page 112 in the PDF for (pictorial) proof that it works.

This should be considered a critical risk, with working exploit available.

I urge all linux Skype users to not leave their Skype clients running full time.

the only fix you will have the choice to - at least till end of the year:
http://forum.skype.com/viewtopic.php?t=475...start=75#233123

I'm okay with Skype not updating the client (well, I say okay), since it's their software and they have no obligations to update it. However, I'm drawing the line at serious security flaws that are open, demonstrated to be exploitable, trivial to fix (it's just one more check on the input) and yet there is no fix coming. In this circumstance I can only recommend to all those that I know (at least those on Linux) to not use Skype because it's a security risk. I'd imagine that most corporations would just banned it outright, if it's not already.

Guys, please, please don't spread security scares unless you've checked out your facts. If this is a brand new Skype vulnerability that Phillip Biondi has discovered and which has now been well publicized since Black Hat, then perhaps you should quote the CVE number for it?

As it turns out, it's almost certainly CAN-2005-3267, which was fixed in version 1.2.0.17 for linux. They were using it as an example to show what might be possible if another similar vulnerability were to be found...