lib/thumbshooter.rb in the Thumbshooter 0.1.5 gem for Ruby allows remote attackers to execute arbitrary commands via shell metacharacters in a URL.
http://www.openwall.com/lists/oss-security/2013/03/26/3
http://www.openwall.com/lists/oss-security/2013/03/26/13
http://vapid.dhs.org/advisories/thumbshooter-ruby-gem-remoteexec.html