Xen 4.2.x, 4.1.x, and earlier, when the hypervisor is running "under memory pressure" and the Xen Security Module (XSM) is enabled, uses the wrong ordering of operations when extending the per-domain event channel tracking table, which causes a use-after-free and allows local guest kernels to inject arbitrary events and gain privileges via unspecified vectors.
http://lists.opensuse.org/opensuse-security-announce/2014-03/msg00015.html
http://lists.opensuse.org/opensuse-security-announce/2014-03/msg00021.html
http://lists.opensuse.org/opensuse-security-announce/2014-04/msg00000.html
http://lists.opensuse.org/opensuse-updates/2013-06/msg00049.html
http://lists.xen.org/archives/html/xen-announce/2013-04/msg00000.html
http://secunia.com/advisories/52857
http://secunia.com/advisories/55082
http://security.gentoo.org/glsa/glsa-201309-24.xml
https://exchange.xforce.ibmcloud.com/vulnerabilities/83226