CVE-2026-20817: Microsoft Windows 10 21h2

High severity, CVSS 7.8. EPSS: 5.4% chance of exploitation in the next 30 days.

Improper handling of insufficient permissions or privileges in Windows Error Reporting allows an authorized attacker to elevate privileges locally.

Affected products

• 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 11 23h2: before 10.0.22631.6491 (fixed in 10.0.22631.6491)
• Microsoft Windows 11 24h2: before 10.0.26100.7623 (fixed in 10.0.26100.7623)
• Microsoft Windows 11 25h2: before 10.0.26200.7623 (fixed in 10.0.26200.7623)
• Microsoft Windows Server 2022: before 10.0.20348.4648 (fixed in 10.0.20348.4648)
• Microsoft Windows Server 2022 23h2: before 10.0.25398.2092 (fixed in 10.0.25398.2092)
• Microsoft Windows Server 2025: before 10.0.26100.32230 (fixed in 10.0.26100.32230)

Published 2026-01-13. Last modified 2026-07-30.