A flaw was found in the way KVM hypervisor handled x2APIC Machine Specific Rregister (MSR) access with nested(=1) virtualization enabled. In that, L1 guest could access L0's APIC register values via L2 guest, when 'virtualize x2APIC mode' is enabled. A guest could use this flaw to potentially crash the host kernel resulting in DoS issue. Kernel versions from 4.16 and newer are vulnerable to this issue.
Exploitability
AV:LAC:HPR:LUI:NScope
S:CImpact
C:NI:NA:H5.6/CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:HAccess Control