I was just reading about this vulnerability in Apache (the web server that pretty much owns the internet). Quite nasty, a single machine can crash a web server with a simple http request. The Apache guys are scrambling for a fix which should be out in the next few days but until then there are a bunch of things you can do to mitigate the bug.
Guess which web server I'm running on this box... <gulp!>
UPDATE: And it's fixed - go get your apt-get update on.