Time-of-Check Time-of-Use Race Condition in Windows Ancillary Function Driver
CVE-2026-20831

7.8HIGH

Key Information:

Vendor

Microsoft
Status
Windows 10 Version 1607
Windows 10 Version 1809
Windows 10 Version 21h2
Windows 10 Version 22h2
Vendor
CVE Published:
13 January 2026

What is CVE-2026-20831?

A time-of-check time-of-use (TOCTOU) race condition exists in the Windows Ancillary Function Driver for WinSock. This vulnerability allows an authorized attacker to exploit the race condition to gain elevated privileges locally. This situation can lead to unauthorized changes in system properties and integrity risks. Mitigation requires patching to address this vulnerability effectively.

Affected Version(s)

Windows 10 Version 1607 32-bit Systems 10.0.14393.0 < 10.0.14393.8783

Windows 10 Version 1809 32-bit Systems 10.0.17763.0 < 10.0.17763.8276

Windows 10 Version 21H2 32-bit Systems 10.0.19044.0 < 10.0.19044.6809

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE...
vendor-advisorypatch

CVSS V3.1

Score:
7.8
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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