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. Linux kernel built with the Kernel-based Virtual Machine (CONFIG_KVM) support was vulnerable to an incorrect segment selector(SS) value error. The error could occur while loading values into the SS register in long mode. A user or process inside a guest could use this flaw to crash the guest, resulting in DoS or potentially escalate their privileges inside the guest.
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