Xen 4.0.x and 4.1.x incorrectly releases a grant reference when releasing a non-v1, non-transitive grant, which allows local guest administrators to cause a denial of service (host crash), obtain sensitive information, or possibly have other impacts via unspecified vectors.
http://www.securitytracker.com/id/1028459
http://www.securityfocus.com/bid/59293
http://www.openwall.com/lists/oss-security/2013/04/18/9
http://www.debian.org/security/2013/dsa-2666
http://security.gentoo.org/glsa/glsa-201309-24.xml
http://secunia.com/advisories/55082
http://lists.opensuse.org/opensuse-security-announce/2014-03/msg00021.html
http://lists.fedoraproject.org/pipermail/package-announce/2013-May/104537.html