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Vulnerabilities

Vulnerability · CVE-2026-21242

Use after free in Windows Subsystem for Linux allows an authorized attacker to elevate privileges locally.

Published Feb 10, 2026 · catalog updated Aug 19, 2026 · Microsoft Windows 10 Version 21H2

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-21242. EPSS is 0.36%. Act only if a listed version of Microsoft Windows 10 Version 21H2 is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High7.0
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.36%
Remediation
Version ranges on file
Affected products
vendor Microsoft Windows 10 Version 21H2 10.0.19044.0 <10.0.19044.6937

Use after free in Windows Subsystem for Linux allows an authorized attacker to elevate privileges locally.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor Microsoft Windows 10 Version 21H2 10.0.19044.0 <10.0.19044.693710.0.19044.0 <10.0.19044.6937

How to fix CVE-2026-21242

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-21242. EPSS is 0.36%. Act only if a listed version of Microsoft Windows 10 Version 21H2 is installed.

Which versions are affected?

Compare what you have installed with Microsoft Windows 10 Version 21H2 10.0.19044.0 <10.0.19044.6937 10.0.19044.0 <10.0.19044.6937. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.36%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Windows security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 10, 2026 · EUVD

    Detected

    Use after free in Windows Subsystem for Linux allows an authorized attacker to elevate privileges locally.

  2. Aug 19, 2026 · EUVD

    Updated

    Use after free in Windows Subsystem for Linux allows an authorized attacker to elevate privileges locally.

Sources

  • CVE.orgVulnerability recordCVE-2026-21242

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-21242

    30-day exploitation probability 0.36%

    first.org
  • EUVDVulnerability recordEUVD-2026-7353

    Use after free in Windows Subsystem for Linux allows an authorized attacker to elevate privileges locally.

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 6, 2026
  • CVE.orgNov 4, 2026
  • EUVDNov 2, 2026