The Elf parser (libelf) in Xen 4.2.x and earlier allow local guest administrators with certain permissions to have an unspecified impact via a crafted kernel, related to "pointer dereferences" involving unexpected calculations.
http://www.openwall.com/lists/oss-security/2013/06/20/4
http://www.openwall.com/lists/oss-security/2013/06/20/2
http://www.debian.org/security/2014/dsa-3006
http://support.citrix.com/article/CTX138058
http://security.gentoo.org/glsa/glsa-201309-24.xml
http://secunia.com/advisories/55082
http://lists.opensuse.org/opensuse-security-announce/2014-04/msg00000.html
http://lists.opensuse.org/opensuse-security-announce/2014-03/msg00021.html
http://lists.opensuse.org/opensuse-security-announce/2014-03/msg00015.html