Xen 4.0.x, 4.1.x, and 4.2.x does not properly restrict the contents of a XRSTOR, which allows local PV guest users to cause a denial of service (unhandled exception and hypervisor crash) via unspecified vectors.
http://www.openwall.com/lists/oss-security/2013/06/03/2
http://www.debian.org/security/2014/dsa-3006
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