OpenStack Keystone Grizzly before 2013.1, Folsom 2012.1.3 and earlier, and Essex does not properly check if the (1) user, (2) tenant, or (3) domain is enabled when using EC2-style authentication, which allows context-dependent attackers to bypass access restrictions.
https://review.openstack.org/#/c/22321/
https://review.openstack.org/#/c/22320/
https://review.openstack.org/#/c/22319/
https://launchpad.net/keystone/grizzly/2013.1
https://launchpad.net/keystone/+milestone/2012.2.4