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Windows 10 21h2Operating system · Microsoft

CVE-2026-21237

HIGH · 7.0 CVSS v3.1 Published 2026-02-10
Fix available
A fix is available. Upgrade to 10.0.19044.6937 / 10.0.19045.6937 or later.
See remediation →
72/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Subsystem for Linux allows an authorized attacker to elevate privileges locally.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A race condition vulnerability exists in Windows Subsystem for Linux (WSL) where improper synchronization during concurrent execution allows a local authorized attacker to manipulate timing and escalate privileges to higher trust levels.

MitigationApply Microsoft security updates for WSL when available; follow least-privilege principles and limit local user access to reduce attack surface.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Windows 10 21h2Operating system
Affected:< 10.0.19044.6937
Windows 10 22h2Operating system
Affected:< 10.0.19045.6937
Windows 11 23h2Operating system
Affected:< 10.0.22631.6649
Windows 11 24h2Operating system
Affected:< 10.0.26100.7781
Windows 11 25h2Operating system
Affected:< 10.0.26200.7781
Windows Server 2022Operating system
Affected:< 10.0.20348.4711
Windows Server 2022 23h2Operating system
Affected:< 10.0.25398.2149
Windows Server 2025Operating system
Affected:< 10.0.26100.32313

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify WSL is installed
    Run `wsl --status` or check for WSL in optional features via `Get-WindowsOptionalFeature -Online -FeatureName Microsoft-Windows-Subsystem-Linux`
    Affected if WSL is installed and enabled on the system
  2. Check Windows 10 build version
    Run `winver` or `systeminfo | findstr /B /C:"OS Version"` to obtain the build number
    Affected if Running Windows 10 21h2 (build < 19044.6937) or Windows 10 22h2 (build < 19045.6937)
  3. Check Windows 11 build version
    Run `winver` or `systeminfo | findstr /B /C:"OS Version"` to obtain the build number
    Affected if Running Windows 11 23h2 (build < 22631.6649), Windows 11 24h2 (build < 26100.7781), or Windows 11 25h2 (build < 26200.7781)
  4. Check Windows Server build version
    Run `systeminfo` or check `winrm` output to obtain the build number
    Affected if Running Windows Server 2022 (build < 20348.4711), Server 2022 23h2 (build < 25398.2149), or Server 2025 (build < 26100.32313)

If WSL is installed on a Windows or Windows Server version with a build number lower than the thresholds listed above, the system is affected by this vulnerability.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 10.0.19044.6937 / 10.0.19045.6937 / 10.0.20348.4711 or later
Fixed in 10.0.19044.693710.0.19045.693710.0.20348.4711
Interim mitigation

Apply Microsoft security updates for WSL when available; follow least-privilege principles and limit local user access to reduce attack surface.

Recommended fix High confidence

Windows 10 21h2: build 10.0.19044.6937 | Windows 10 22h2: build 10.0.19045.6937 | Windows 11 23h2: build 10.0.22631.6649 | Windows 11 24h2: build 10.0.26100.7781 | Windows 11 25h2: build 10.0.26200.7781 | Windows Server 2022: build 10.0.20348.4711 | Windows Server 2022 23h2: build 10.0.25398.2149 |

  1. 1. Identify current Windows build version by running 'winver' or 'systeminfo | findstr /B /C:"OS Version"'
  2. 2. For Windows 10 21h2 (build < 10.0.19044.6937): Install KB5055523 or later to reach build 10.0.19044.6937
  3. 3. For Windows 10 22h2 (build < 10.0.19045.6937): Install KB5055523 or later to reach build 10.0.19045.6937
  4. 4. For Windows 11 23h2 (build < 10.0.22631.6649): Install KB5055523 or later to reach build 10.0.22631.6649
  5. 5. For Windows 11 24h2 (build < 10.0.26100.7781): Install KB5055523 or later to reach build 10.0.26100.7781
  6. 6. For Windows 11 25h2 (build < 10.0.26200.7781): Install KB5055523 or later to reach build 10.0.26200.7781
  7. 7. For Windows Server 2022 (build < 10.0.20348.4711): Install KB5055523 or later to reach build 10.0.20348.4711
  8. 8. For Windows Server 2022 23h2 (build < 10.0.25398.2149): Install KB5055523 or later to reach build 10.0.25398.2149
Caveat Standard Windows cumulative update risks apply - review KB5055523 release notes for any known issues before deployment in production environments

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Windows 10 21h2 Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,440
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-21237 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data