The x86_emulate function in arch/x86/x86_emulate/x86_emulate.c in Xen 3.3.x through 4.4.x does not check the supervisor mode permissions for instructions that generate software interrupts, which allows local HVM guest users to cause a denial of service (guest crash) via unspecified vectors.
lists.opensuse.org/opensuse-security-announce/2014-10/msg00002.html
lists.opensuse.org/opensuse-security-announce/2014-10/msg00003.html
secunia.com/advisories/61500
secunia.com/advisories/61858
secunia.com/advisories/61890
security.gentoo.org/glsa/glsa-201412-42.xml
support.citrix.com/article/CTX200218
www.debian.org/security/2014/dsa-3041
www.securityfocus.com/bid/70062
www.securitytracker.com/id/1030889
xenbits.xen.org/xsa/advisory-106.html
lists.fedoraproject.org/pipermail/package-announce/2014-October/140418.html
lists.fedoraproject.org/pipermail/package-announce/2014-October/140483.html