OpenStack Keystone Essex 2012.1.3 and earlier, Folsom 2012.2.3 and earlier, and Grizzly grizzly-2 and earlier allows remote attackers to cause a denial of service (disk consumption) via many invalid token requests that trigger excessive generation of log entries.
https://bugzilla.redhat.com/show_bug.cgi?id=906171
https://bugs.launchpad.net/keystone/+bug/1098307
http://www.ubuntu.com/usn/USN-1715-1
http://www.securityfocus.com/bid/57747
http://rhn.redhat.com/errata/RHSA-2013-0253.html
http://lists.fedoraproject.org/pipermail/package-announce/2013-February/098906.html