The (1) mamcache and (2) KVS token backends in OpenStack Identity (Keystone) Folsom 2012.2.x and Grizzly before 2013.1.4 do not properly compare the PKI token revocation list with PKI tokens, which allow remote attackers to bypass intended access restrictions via a revoked PKI token.
https://bugs.launchpad.net/keystone/+bug/1202952
http://www.ubuntu.com/usn/USN-2002-1
http://secunia.com/advisories/54706
http://seclists.org/oss-sec/2013/q3/586