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Vulnerabilities

Vulnerability · CVE-2026-21236

Heap-based buffer overflow in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

Published Feb 10, 2026 · catalog updated Aug 19, 2026 · Microsoft Windows Server 2025 (Server Core installation)

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-2026-21236. EPSS is 0.44%. Act only if a listed version of Microsoft Windows Server 2025 (Server Core installation) 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
High7.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.44%
Remediation
Version ranges on file
Affected products
vendor Microsoft Windows Server 2025 (Server Core installation) 10.0.26100.0 <10.0.26100.32370

Heap-based buffer overflow in Windows Ancillary Function Driver for WinSock 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 Server 2025 (Server Core installation) 10.0.26100.0 <10.0.26100.3237010.0.26100.0 <10.0.26100.32370

How to fix CVE-2026-21236

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-2026-21236. EPSS is 0.44%. Act only if a listed version of Microsoft Windows Server 2025 (Server Core installation) is installed.

Which versions are affected?

Compare what you have installed with Microsoft Windows Server 2025 (Server Core installation) 10.0.26100.0 <10.0.26100.32370 10.0.26100.0 <10.0.26100.32370. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.44%. 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

    Heap-based buffer overflow in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

  2. Aug 19, 2026 · EUVD

    Updated

    Heap-based buffer overflow in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

Sources

  • CVE.orgVulnerability recordCVE-2026-21236

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-21236

    30-day exploitation probability 0.44%

    first.org
  • EUVDVulnerability recordEUVD-2026-7349

    Heap-based buffer overflow in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

    euvd.enisa.europa.eu
  • urlscan.ioThreat intelligenceCVE-2026-21236
    urlscan.io

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.

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