Vulnerability-Lookup

FKIE_CVE-2026-43265

Vulnerability from fkie_nvd - Published: 2026-05-06 12:16 - Updated: 2026-05-08 20:33

Severity ?

5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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 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.

References

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

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*

JSON

To clipboard

{
  "configurations": [
    {
      "nodes": [
        {
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  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Ignore -EBUSY when checking nested events from vcpu_block()\n\nIgnore -EBUSY when checking nested events after exiting a blocking state\nwhile L2 is active, as exiting to userspace will generate a spurious\nuserspace exit, usually with KVM_EXIT_UNKNOWN, and likely lead to the VM\u0027s\ndemise.  Continuing with the wakeup isn\u0027t perfect either, as *something*\nhas gone sideways if a vCPU is awakened in L2 with an injected event (or\nworse, a nested run pending), but continuing on gives the VM a decent\nchance of surviving without any major side effects.\n\nAs explained in the Fixes commits, it _should_ be impossible for a vCPU to\nbe put into a blocking state with an already-injected event (exception,\nIRQ, or NMI).  Unfortunately, userspace can stuff MP_STATE and/or injected\nevents, and thus put the vCPU into what should be an impossible state.\n\nDon\u0027t bother trying to preserve the WARN, e.g. with an anti-syzkaller\nKconfig, as WARNs can (hopefully) be added in paths where _KVM_ would be\nviolating x86 architecture, e.g. by WARNing if KVM attempts to inject an\nexception or interrupt while the vCPU isn\u0027t running."
    }
  ],
  "id": "CVE-2026-43265",
  "lastModified": "2026-05-08T20:33:43.293",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
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  "vulnStatus": "Analyzed",
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  ]
}

CVE-2026-43265 (GCVE-0-2026-43265)

Vulnerability from cvelistv5 – Published: 2026-05-06 11:28 – Updated: 2026-05-11 22:21

Title

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

Summary

Severity ?

No CVSS data available.

Assigner

Linux

References

6 references

URL	Tags
https://git.kernel.org/stable/c/78265cd066d73a5cb…
https://git.kernel.org/stable/c/ec3be7dc9391085a2…
https://git.kernel.org/stable/c/2657439265d34a911…
https://git.kernel.org/stable/c/1e88b5f854bdb4694…
https://git.kernel.org/stable/c/1c957773063ed3264…
https://git.kernel.org/stable/c/ead63640d4e72e6f6…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < 78265cd066d73a5cb41c088fcae4a2515e480d97 (git) Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < ec3be7dc9391085a2d96700e159d66d1328b7ff6 (git) Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < 2657439265d34a911886b916ba8be97ecc117d51 (git) Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < 1e88b5f854bdb469424132e0bb44793ad7a7c20a (git) Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < 1c957773063ed3264953597e32990a748381caf6 (git) Affected: 26844fee6adee9b1557d2279b0506285de9ee82b , < ead63640d4e72e6f6d464f4e31f7fecb79af8869 (git)
Linux	Linux	Affected: 6.1 Unaffected: 0 , < 6.1 (semver) Unaffected: 6.1.167 , ≤ 6.1.* (semver) Unaffected: 6.6.130 , ≤ 6.6.* (semver) Unaffected: 6.12.77 , ≤ 6.12.* (semver) Unaffected: 6.18.17 , ≤ 6.18.* (semver) Unaffected: 6.19.6 , ≤ 6.19.* (semver) Unaffected: 7.0 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

To clipboard

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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

FKIE_CVE-2026-43265

CVE-2026-43265 (GCVE-0-2026-43265)

Tags

Sightings

Nomenclature