The parsing engine in Clam AntiVirus versions below 0.95 can be bypassed by manipulating RAR archives in a certain way that ClamAV cannot extract the content but the end user is able to.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/76301/TZO-05-2009.txt
Source: https://packetstormsecurity.com/files/76301/ClamAV-Evasion.html