CVE-2026-20810: Microsoft Windows 10 1809

High severity, CVSS 7.8. EPSS: 0.5% chance of exploitation in the next 30 days.

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

Affected products

• Microsoft Windows 10 1809: before 10.0.17763.8276 (fixed in 10.0.17763.8276)
• Microsoft Windows 10 21h2: before 10.0.19044.6809 (fixed in 10.0.19044.6809)
• Microsoft Windows 10 22h2: before 10.0.19045.6809 (fixed in 10.0.19045.6809)
• Microsoft Windows Server 2019: before 10.0.17763.8276 (fixed in 10.0.17763.8276)

Published 2026-01-13. Last modified 2026-06-17.