arch/x86/kvm/svm/nested.c in the Linux kernel before 5.11.12 has a use-after-free in which an AMD KVM guest can bypass access control on host OS MSRs when there are nested guests, aka CID-a58d9166a756. This occurs because of a TOCTOU race condition associated with a VMCB12 double fetch in nested_svm_vmrun.
5.3.0-18.195.3.0-24.265.4.0-9.126.5.0-9.95.13.0-19.194.13.0-16.194.15.0-1001.15.3.0-1003.35.3.0-1008.95.3.0-1009.105.3.0-1010.115.4.0-1005.55.13.0-1005.66.5.0-1008.85.0.0-1021.24~18.04.15.0.0-1022.25~18.04.15.0.0-1023.26~18.04.15.0.0-1024.27~18.04.15.0.0-1025.285.0.0-1027.305.11.0-1009.9~20.04.2Exploitability
AV:LAC:HPR:NUI:NScope
S:UImpact
C:HI:HA:HCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H