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.
Exploitability
AV:LAC:HPR:LUI:NScope
S:UImpact
C:HI:HA:H7/CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:HConfiguration