PyGIT.py in the Trac Git plugin (trac-git) before 0.0.20080710-3+lenny1 and before 0.0.20090320-1 on Debian GNU/Linux, when enabled in Trac, allows remote attackers to execute arbitrary commands via shell metacharacters in a crafted HTTP query that is used to generate a certain git command.
https://exchange.xforce.ibmcloud.com/vulnerabilities/56105
http://www.securityfocus.com/bid/38076
http://www.debian.org/security/2010/dsa-1990