The PV pagetable code in arch/x86/mm.c in Xen 4.7.x and earlier allows local 32-bit PV guest OS administrators to gain host OS privileges by leveraging fast-paths for updating pagetable entries.
support.citrix.com/article/CTX214954
www.debian.org/security/2016/dsa-3633
www.oracle.com/technetwork/topics/security/ovmbulletinjul2016-3090546.html
www.securityfocus.com/bid/92131
www.securitytracker.com/id/1036446
xenbits.xen.org/xsa/advisory-182.html
xenbits.xen.org/xsa/xsa182-4.5.patch
xenbits.xen.org/xsa/xsa182-4.6.patch
xenbits.xen.org/xsa/xsa182-unstable.patch
security.gentoo.org/glsa/201611-09