The HVMOP_set_mem_type control in Xen 4.1 through 4.4.x allows local guest HVM administrators to cause a denial of service (hypervisor crash) or possibly execute arbitrary code by leveraging a separate qemu-dm vulnerability to trigger invalid page table translations for unspecified memory page types.
http://xenbits.xen.org/xsa/advisory-92.html
http://www.securitytracker.com/id/1030160
http://www.securityfocus.com/bid/67113
http://www.openwall.com/lists/oss-security/2014/04/30/10
http://www.openwall.com/lists/oss-security/2014/04/29/1
http://www.debian.org/security/2014/dsa-3006
http://security.gentoo.org/glsa/glsa-201407-03.xml
http://lists.opensuse.org/opensuse-security-announce/2014-10/msg00003.html
http://lists.fedoraproject.org/pipermail/package-announce/2014-May/133191.html
http://lists.fedoraproject.org/pipermail/package-announce/2014-May/133148.html