MSRC-CVE-2026-20810 — Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

Summary

Impact: Elevation of Privilege. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.

Details

What privileges could be gained by an attacker who successfully exploited this vulnerability?
An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.

Security updates
10.0.17763.8276 — https://support.microsoft.com/help/5073723
10.0.19044.6809 — https://support.microsoft.com/help/5073724

Vulnerabilities 1

High 7.8

CVE-2026-20810

Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

Free of memory not on the heap in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

Microsoft Windows Server 2019 Windows Server 2019 (Server Core installation) Windows 10 Version 1809 Windows

Jan 13, 2026

Revision history

2026-01-13 #1
Information published.

References

CVE-2026-20810 Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20810
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss