The virSecurityManagerSetProcessLabel function in libvirt 0.10.2.7, 1.0.5.5, and 1.1.1, when the domain has read an uid:gid label, does not properly set group memberships, which allows local users to gain privileges.
https://bugzilla.redhat.com/show_bug.cgi?id=1006509
http://wiki.libvirt.org/page/Maintenance_Releases
http://libvirt.org/git/?p=libvirt.git%3Ba=commitdiff%3Bh=fe11d34a6d46d6641ce90dc665164fda7bb6bff8