---
id: CVE-2026-43265
title: 'KVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()'
summary: |-
  In 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 e…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b <
    78265cd066d73a5cb41c088fcae4a2515e480d97
  - >-
    Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b <
    ec3be7dc9391085a2d96700e159d66d1328b7ff6
  - >-
    Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b <
    2657439265d34a911886b916ba8be97ecc117d51
  - >-
    Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b <
    1e88b5f854bdb469424132e0bb44793ad7a7c20a
  - >-
    Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b <
    1c957773063ed3264953597e32990a748381caf6
  - >-
    Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b <
    ead63640d4e72e6f6d464f4e31f7fecb79af8869
  - Linux 6.1
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T15:32:33.106636Z'
published: '2026-05-06'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T15:42:45.276Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-43265'
references:
  - url: 'https://git.kernel.org/stable/c/78265cd066d73a5cb41c088fcae4a2515e480d97'
  - url: 'https://git.kernel.org/stable/c/ec3be7dc9391085a2d96700e159d66d1328b7ff6'
  - url: 'https://git.kernel.org/stable/c/2657439265d34a911886b916ba8be97ecc117d51'
  - url: 'https://git.kernel.org/stable/c/1e88b5f854bdb469424132e0bb44793ad7a7c20a'
  - url: 'https://git.kernel.org/stable/c/1c957773063ed3264953597e32990a748381caf6'
  - url: 'https://git.kernel.org/stable/c/ead63640d4e72e6f6d464f4e31f7fecb79af8869'
tags:
  - cve.org
epss: 0.00119
epssPercentile: 0.0178
ingestedAt: '2026-11-06T15:54:03.957Z'
---

## Overview

In 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.

## Affected

- `Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b < 78265cd066d73a5cb41c088fcae4a2515e480d97`
- `Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b < ec3be7dc9391085a2d96700e159d66d1328b7ff6`
- `Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b < 2657439265d34a911886b916ba8be97ecc117d51`
- `Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b < 1e88b5f854bdb469424132e0bb44793ad7a7c20a`
- `Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b < 1c957773063ed3264953597e32990a748381caf6`
- `Linux >= 26844fee6adee9b1557d2279b0506285de9ee82b < ead63640d4e72e6f6d464f4e31f7fecb79af8869`
- `Linux 6.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.