Local privilege escalation via WinSock driver race
Published Jan 13, 2026 · Updated Jan 13, 2026
A TOCTOU race in Microsoft Windows Ancillary Function Driver for WinSock allows local users to elevate privileges. Microsoft identifies a time-of-check time-of-use race in the AFD kernel driver but has not disclosed the checked object or the state change that wins the race. Successful exploitation requires low-privileged local access and grants elevated control over the affected Windows host.
Summary
What happened
A TOCTOU race in Microsoft Windows Ancillary Function Driver for WinSock allows local users to elevate privileges. Microsoft identifies a time-of-check time-of-use race in the AFD kernel driver but has not disclosed the checked object or the state change that wins the race. Successful exploitation requires low-privileged local access and grants elevated control over the affected Windows host.
The record
- CVE
- CVE-2026-20831
- Published
- Jan 13, 2026
- Updated
- Jan 13, 2026
- Vendor
- Microsoft
- Product
- Windows Server 2019
- Classifications
- CWE-367, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Jan 13, 2026CVE publishedPublication date reported by the CVE source.
- Jan 13, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.0.17763.0 <10.0.17763.8276
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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