CVE-2026-21237

Local privilege escalation via WSL race condition

Published Feb 10, 2026 · Updated Feb 10, 2026

Race condition in Windows Subsystem for Linux on affected Windows releases allows local users to elevate privileges on the host. Microsoft identifies improper synchronization and use-after-free but does not disclose the affected WSL object, code path, or competing operations. A low-privileged local user must win the race; successful exploitation grants elevated privileges with host-level data and service control.

CVSS severity7.0
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in Windows Subsystem for Linux on affected Windows releases allows local users to elevate privileges on the host. Microsoft identifies improper synchronization and use-after-free but does not disclose the affected WSL object, code path, or competing operations. A low-privileged local user must win the race; successful exploitation grants elevated privileges with host-level data and service control.

The record

CVE
CVE-2026-21237
Published
Feb 10, 2026
Updated
Feb 10, 2026
Vendor
Microsoft
Product
Windows Server 2025 (Server Core installation)
Classifications
CWE-362, CWE-416, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.26100.0 <10.0.26100.32370

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server 2025 (Server Core installation)version=10.0.26100.0 <10.0.26100.32370
Microsoft · Windows 11, version 25H2version=10.0.26200.0 <10.0.26200.7840
Microsoft · Windows 11, version 24H2version=10.0.26100.0 <10.0.26100.7840
Microsoft · Windows 10 Version 21H2version=10.0.19044.0 <10.0.19044.6937
Microsoft · Windows Server 2022, 23H2 Edition (Server Core installation)version=10.0.25398.0 <10.0.25398.2149
Microsoft · Windows 11 Version 22H3version=10.0.22631.0 <10.0.22631.6649
Microsoft · Windows 10 Version 22H2version=10.0.19045.0 <10.0.19045.6937
Microsoft · Windows 11, version 26H1version=10.0.28000.0 <10.0.28000.1575
Microsoft · Windows 11 Version 23H2version=10.0.22631.0 <10.0.22631.6649
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.4773
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.32370

Published CVSS scores

7.0MicrosoftCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CWE-416Use After Free
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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