The Sheepdog backend in OpenStack Image Registry and Delivery Service (Glance) 2013.2 before 2013.2.4 and icehouse before icehouse-rc2 allows remote authenticated users with permission to insert or modify an image to execute arbitrary commands via a crafted location.
https://launchpad.net/bugs/1298698
http://www.ubuntu.com/usn/USN-2193-1