KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()

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Summary

CVECVE-2026-43265
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-06 12:16:47 UTC
Updated2026-05-08 20:33:43 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block() Ignore -EBUSY when checking nested events after exiting a blocking state while L2 is active, as exiting to userspace will generate a spurious userspace exit, usually with KVM_EXIT_UNKNOWN, and likely lead to the VM's demise. Continuing with the wakeup isn't perfect either, as *something* has gone sideways if a vCPU is awakened in L2 with an injected event (or worse, a nested run pending), but continuing on gives the VM a decent chance of surviving without any major side effects. As explained in the Fixes commits, it _should_ be impossible for a vCPU to be put into a blocking state with an already-injected event (exception, IRQ, or NMI). Unfortunately, userspace can stuff MP_STATE and/or injected events, and thus put the vCPU into what should be an impossible state. Don't bother trying to preserve the WARN, e.g. with an anti-syzkaller Kconfig, as WARNs can (hopefully) be added in paths where _KVM_ would be violating x86 architecture, e.g. by WARNing if KVM attempts to inject an exception or interrupt while the vCPU isn't running.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: NVD-CWE-noinfo

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 26844fee6adee9b1557d2279b0506285de9ee82b 78265cd066d73a5cb41c088fcae4a2515e480d97 git Not specified
CNA Linux Linux affected 26844fee6adee9b1557d2279b0506285de9ee82b ec3be7dc9391085a2d96700e159d66d1328b7ff6 git Not specified
CNA Linux Linux affected 26844fee6adee9b1557d2279b0506285de9ee82b 2657439265d34a911886b916ba8be97ecc117d51 git Not specified
CNA Linux Linux affected 26844fee6adee9b1557d2279b0506285de9ee82b 1e88b5f854bdb469424132e0bb44793ad7a7c20a git Not specified
CNA Linux Linux affected 26844fee6adee9b1557d2279b0506285de9ee82b 1c957773063ed3264953597e32990a748381caf6 git Not specified
CNA Linux Linux affected 26844fee6adee9b1557d2279b0506285de9ee82b ead63640d4e72e6f6d464f4e31f7fecb79af8869 git Not specified
CNA Linux Linux affected 6.1 Not specified
CNA Linux Linux unaffected 6.1 semver Not specified
CNA Linux Linux unaffected 6.1.167 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.130 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.77 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.17 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.6 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/ec3be7dc9391085a2d96700e159d66d1328b7ff6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/2657439265d34a911886b916ba8be97ecc117d51 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/78265cd066d73a5cb41c088fcae4a2515e480d97 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/1c957773063ed3264953597e32990a748381caf6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/1e88b5f854bdb469424132e0bb44793ad7a7c20a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/ead63640d4e72e6f6d464f4e31f7fecb79af8869 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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