Description
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.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | linux | 5.10.28-1 | — |
| Debian 13 | linux | 5.10.28-1 | — |
| Debian 12 | linux | 5.10.28-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | linux-oem-5.10 | 5.10.0-1025.26 | USN-4948-1 |
| Ubuntu 20.04 LTS | linux-riscv +1 | No fix yet | — |
| Ubuntu 18.04 LTS | linux-gcp +13 | No fix yet | — |
| Ubuntu 16.04 LTS | linux-hwe-edge | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | perf +26 | 4.18.0-348.el8 | RHSA-2021:4356 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 2 (CBL-Mariner) | kernel | 5.10.78.1-1 | — |
Advisories 2
- RHSA-2021:4356 Red Hat Security Advisory: kernel security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Oct 2, 2026
- USN-4948-1 linux-oem-5.10 vulnerabilities Ubuntu Security Notices (USN) · Jun 3, 2026
References
- http://packetstormsecurity.com/files/163324/KVM-nested_svm_vmrun-Double-Fetch.html
- https://bugs.chromium.org/p/project-zero/issues/detail?id=2177
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a58d9166a756a0f4a6618e4f593232593d6df134
- https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.12
- https://security.netapp.com/advisory/ntap-20210902-0008/