The L3-agent in OpenStack Neutron before 2013.2.4, 2014.x before 2014.1.2, and Juno before Juno-2 allows remote authenticated users to cause a denial of service (IPv4 address attachment outage) by attaching an IPv6 private subnet to a L3 router.
https://bugs.launchpad.net/neutron/+bug/1309195
http://www.ubuntu.com/usn/USN-2255-1