OpenStack Compute (Nova) Folsom, Grizzly, and Havana does not properly verify the virtual size of a QCOW2 image, which allows local users to cause a denial of service (host file system disk consumption) via a compressed QCOW2 image. NOTE: this issue is due to an incomplete fix for CVE-2013-2096.
https://bugs.launchpad.net/nova/+bug/1206081
http://www.ubuntu.com/usn/USN-2247-1