A flaw was found in the way Linux kernel KVM hypervisor before 4.18 emulated instructions such as sgdt/sidt/fxsave/fxrstor. It did not check current privilege(CPL) level while emulating unprivileged instructions. An unprivileged guest user/process could use this flaw to potentially escalate privileges inside guest.
- https://usn.ubuntu.com/3777-1/
- https://usn.ubuntu.com/3777-2/
- https://github.com/ARPSyndicate/cvemon