The load_segment_descriptor implementation in arch/x86/kvm/emulate.c in the Linux kernel before 4.9.5 improperly emulates a “MOV SS, NULL selector” instruction, which allows guest OS users to cause a denial of service (guest OS crash) or gain guest OS privileges via a crafted application.
git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=33ab91103b3415e12457e3104f0e4517ce12d0f3
www.debian.org/security/2017/dsa-3791
www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.9.5
www.openwall.com/lists/oss-security/2017/01/19/2
www.securityfocus.com/bid/95673
access.redhat.com/errata/RHSA-2017:1615
access.redhat.com/errata/RHSA-2017:1616
bugzilla.redhat.com/show_bug.cgi?id=1414735
github.com/torvalds/linux/commit/33ab91103b3415e12457e3104f0e4517ce12d0f3
usn.ubuntu.com/3754-1/