Jan 2026: Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
CVE-2026-20831 Published on January 13, 2026
Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability
Time-of-check time-of-use (toctou) race condition in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.
Weakness Type
What is a TOCTTOU Vulnerability?
The software checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the software to perform invalid actions when the resource is in an unexpected state. This weakness can be security-relevant when an attacker can influence the state of the resource between check and use. This can happen with shared resources such as files, memory, or even variables in multithreaded programs.
CVE-2026-20831 has been classified to as a TOCTTOU vulnerability or weakness.
Products Associated with CVE-2026-20831
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Affected Versions
Microsoft Windows 10 Version 1607:- Version 10.0.14393.0 and below 10.0.14393.8783 is affected.
- Version 10.0.17763.0 and below 10.0.17763.8276 is affected.
- Version 10.0.19044.0 and below 10.0.19044.6809 is affected.
- Version 10.0.19045.0 and below 10.0.19045.6809 is affected.
- Version 10.0.22631.0 and below 10.0.22631.6491 is affected.
- Version 10.0.22631.0 and below 10.0.22631.6491 is affected.
- Version 10.0.26100.0 and below 10.0.26100.7623 is affected.
- Version 10.0.26200.0 and below 10.0.26200.7623 is affected.
- Version 6.1.7601.0 and below 6.1.7601.28117 is affected.
- Version 6.1.7601.0 and below 6.1.7601.28117 is affected.
- Version 6.0.6003.0 and below 6.0.6003.23717 is affected.
- Version 6.0.6003.0 and below 6.0.6003.23717 is affected.
- Version 6.2.9200.0 and below 6.2.9200.25868 is affected.
- Version 6.2.9200.0 and below 6.2.9200.25868 is affected.
- Version 6.3.9600.0 and below 6.3.9600.22968 is affected.
- Version 6.3.9600.0 and below 6.3.9600.22968 is affected.
- Version 10.0.14393.0 and below 10.0.14393.8783 is affected.
- Version 10.0.14393.0 and below 10.0.14393.8783 is affected.
- Version 10.0.17763.0 and below 10.0.17763.8276 is affected.
- Version 10.0.17763.0 and below 10.0.17763.8276 is affected.
- Version 10.0.20348.0 and below 10.0.20348.4648 is affected.
- Version 10.0.25398.0 and below 10.0.25398.2092 is affected.
- Version 10.0.26100.0 and below 10.0.26100.32230 is affected.
- Version 10.0.26100.0 and below 10.0.26100.32230 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.