CVE-2021-40449: Microsoft Windows Win32k Privilege Escalation Vulnerability

High severity, CVSS 7.8. Actively exploited: in CISA KEV since 2021-11-17. EPSS: 74.1% chance of exploitation in the next 30 days.

Win32k Elevation of Privilege Vulnerability

Affected products

• Microsoft Windows 10 1507: before 10.0.10240.19086 (fixed in 10.0.10240.19086)
• Microsoft Windows 10 1607: before 10.0.14393.4704 (fixed in 10.0.14393.4704)
• Microsoft Windows 10 1809: before 10.0.17763.2237 (fixed in 10.0.17763.2237)
• Microsoft Windows 10 1909: before 10.0.18363.1854 (fixed in 10.0.18363.1854)
• Microsoft Windows 10 2004: before 10.0.19041.1288 (fixed in 10.0.19041.1288)
• Microsoft Windows 10 20h2: before 10.0.19041.1288 (fixed in 10.0.19041.1288)
• Microsoft Windows 10 21h1: before 10.0.19041.1288 (fixed in 10.0.19041.1288)
• Microsoft Windows 11: any version
• Microsoft Windows 11 21h2: before 10.0.22000.258 (fixed in 10.0.22000.258)
• Microsoft Windows 7: affected versions not specified
• Microsoft Windows 8.1: affected versions not specified
• Microsoft Windows Rt 8.1: affected versions not specified
• Microsoft Windows Server 2004: before 10.0.19041.1288 (fixed in 10.0.19041.1288)
• Microsoft Windows Server 2008: affected versions not specified; version r2 only
• Microsoft Windows Server 2012: affected versions not specified; version r2 only
• Microsoft Windows Server 2016: before 10.0.14393.4704 (fixed in 10.0.14393.4704)
• Microsoft Windows Server 2019: before 10.0.17763.2237 (fixed in 10.0.17763.2237)
• Microsoft Windows Server 2022: before 10.0.20348.288 (fixed in 10.0.20348.288)
• Microsoft Windows Server 20h2: before 10.0.19042.1288 (fixed in 10.0.19042.1288)

Published 2021-10-13. Last modified 2026-06-17.