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CVE-2026-72239
x86/virt/sev: Revert "Drop WBINVD before setting MSR_AMD64_SYSCFG_SNP_EN"
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem arch/x86. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72239 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Revert 99cf1fb58e68 ("x86/virt/sev: Drop WBINVD before setting MSR_AMD64_SYSCFG_SNP_EN"). Section 8.8 of the SNP spec says: Before invoking SNP_INIT_EX with INIT_RMP set to 1, software must ensure that no CPUs contain dirty cache lines for the memory containing the RMP. Cachelines can be moved from cache to cache in a dirty state. The wbinvd_on_all_cpus() before SNP_INIT_EX flushes the caches for each CPU, but if the IPIs for WBINVD race with this dirty cacheline movement, it is possible that they may not get flushed, violating the firmware requirement. Doing wbinvd_on_all_cpus() before setting SNPEn is safer since the RMP table is not yet in use. [ Heroically bisected by Srikanth. ] [ bp: Massage commit message. ]
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
arch/x86/virt/svm/sev.c
- What this is
- X86 ARCHITECTURE (32-BIT AND 64-BIT)MAINTAINERS section matched on arch/x86/ · linux-kernel@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_KVM_AMD_SEV /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookworm?
- trixieYnot built on amd64/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidYnot built on amd64/cloud-amd64, arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- ?
- not established - no Makefile entry for the affected file
- Y
- built in where it is built at all; some flavours do not build it
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switch
- CONFIG_KVM_AMD_SEV
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- 9.3 critical
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.18%, higher than 7.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- arch/x86
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 7.1 | 7.1.5 | e5158ff53fdf |
| 7.1 | 7.2 | 4c2509f3b797 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The flaw is in host-side SNP platform initialization via snp_prepare(), reached only during local boot-time KVM/SEV setup or privileged KVM_SEV_INIT/ioctl paths on /dev/kvm and /dev/sev, not from any network-facing handler.
- AC:LAttack complexity, low
- The missing pre-SNPEn WBINVD creates a race where later WBINVD IPIs can miss dirty RMP cachelines; an attacker who can drive concurrent CPU/cache activity during init can influence this timing, and when uncertain we choose Low.
- PR:NPrivileges required, none
- On typical SEV-SNP cloud hosts SNP init runs automatically at boot, so a malicious confidential VM tenant needs no host privileges to exploit latent incorrect RMP state that breaks guest/host memory isolation.
- UI:NUser interaction, none
- Exploitation does not require any victim user action such as opening files or mounting filesystems; the vulnerable initialization runs during host boot or privileged hypervisor setup without end-user interaction.
- S:CScope, changed
- Corrupt or inconsistent RMP initialization undermines the SEV-SNP memory-isolation boundary between confidential guests and the hypervisor, enabling cross-boundary impact beyond the initializing kernel component's security scope.
- C:HConfidentiality impact, high
- Incorrect RMP table state from unflushed dirty cachelines can break private/shared page tracking and allow unauthorized reads of host or other guest memory across the confidentiality boundary on affected AMD SEV-SNP systems.
- I:HIntegrity impact, high
- RMP metadata corruption can mislabel page ownership and permissions, potentially permitting unauthorized writes or guest-controlled modification of hypervisor memory and enabling further compromise of the isolation model.
- A:HAvailability impact, high
- Violating RMP initialization requirements can trigger fatal RMP faults (#PF) that crash the host kernel, and SNP init failures or inconsistent RMP state can deny availability of confidential VM services.