Xen 4.2.x and 4.3.x, when using Intel VT-d for PCI passthrough, does not properly flush the TLB after clearing a present translation table entry, which allows local guest administrators to cause a denial of service or gain privileges via unspecified vectors related to an "inverted boolean parameter."
http://www.securitytracker.com/id/1029369
http://www.openwall.com/lists/oss-security/2013/11/21/1
http://www.openwall.com/lists/oss-security/2013/11/20/3
http://security.gentoo.org/glsa/glsa-201407-03.xml
http://lists.opensuse.org/opensuse-updates/2013-12/msg00059.html