The mod_l2_entry function in arch/x86/mm.c in Xen 3.4 through 4.6.x does not properly validate level 2 page table entries, which allows local PV guest administrators to gain privileges via a crafted superpage mapping.
lists.fedoraproject.org/pipermail/package-announce/2015-November/171082.html
lists.fedoraproject.org/pipermail/package-announce/2015-November/171185.html
lists.fedoraproject.org/pipermail/package-announce/2015-November/171249.html
lists.opensuse.org/opensuse-updates/2015-11/msg00063.html
lists.opensuse.org/opensuse-updates/2015-12/msg00053.html
support.citrix.com/article/CTX202404
www.debian.org/security/2015/dsa-3390
www.securityfocus.com/bid/77366
www.securitytracker.com/id/1034032
xenbits.xen.org/xsa/advisory-148.html
github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-022-2015.txt
security.gentoo.org/glsa/201604-03