Xen 3.4 through 4.2, and possibly earlier versions, allows local guest OS administrators to cause a denial of service (Xen infinite loop and physical CPU consumption) by setting a VCPU with an "inappropriate deadline."
https://security.gentoo.org/glsa/201604-03
https://exchange.xforce.ibmcloud.com/vulnerabilities/80022
http://www.securitytracker.com/id?1027759
http://www.securityfocus.com/bid/56498
http://www.openwall.com/lists/oss-security/2012/11/13/1
http://www.debian.org/security/2012/dsa-2582
http://security.gentoo.org/glsa/glsa-201309-24.xml
http://secunia.com/advisories/55082
http://secunia.com/advisories/51468
http://secunia.com/advisories/51413
http://secunia.com/advisories/51352
http://secunia.com/advisories/51324
http://secunia.com/advisories/51200
http://rhn.redhat.com/errata/RHSA-2012-1540.html
http://lists.xen.org/archives/html/xen-announce/2012-11/msg00001.html
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/2012-12/msg00001.html
http://lists.opensuse.org/opensuse-security-announce/2012-11/msg00018.html
http://lists.opensuse.org/opensuse-security-announce/2012-11/msg00017.html
http://lists.opensuse.org/opensuse-security-announce/2012-11/msg00009.html
http://lists.opensuse.org/opensuse-security-announce/2012-11/msg00008.html