OpenStack Compute (Nova) Folsom, Grizzly, and Havana, when use_cow_images is set to False, does not verify the virtual size of a QCOW2 image, which allows local users to cause a denial of service (host file system disk consumption) by transferring an image with a large virtual size that does not contain a large amount of data from Glance.  NOTE: this issue is due to an incomplete fix for CVE-2013-2096.