The DoCommand function in jhead.c in Matthias Wandel jhead 2.84 and earlier allows attackers to execute arbitrary commands via shell metacharacters in unspecified input.
https://bugs.launchpad.net/ubuntu/+source/jhead/+bug/271020
http://www.securityfocus.com/bid/31921
http://www.openwall.com/lists/oss-security/2008/11/26/4
http://www.openwall.com/lists/oss-security/2008/10/16/3