According to VirusTotal a 5 year old Windows vulnerability is still not detected by Avast! Although the exploit itself was patched by MS, the malware itself that makes use of it should be detected by AV software.
You can read about the vulnerability here
Here you can see the results by VirusTotal.
Now I must admit that this report of VT dates from december 2010, but I reckon that since that’s only a month ago, it’s still not implemented in the virus definitions of Avast! yet.
While many of the other major AV software do detect this, I am kinda surprised Avast! doesn’t yet. Might wanna do something about this, as this vulnerability is still being exploited today!