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CVE-2021-40449: Win32k Elevation of Privilege Vulnerability

• Severity: medium (CVSS 4.6 v2.0)
• Exploited in the wild: yes — in CISA KEV since 2021-11-17
• EPSS: 81.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-10-13 · updated 2026-06-17
• Weakness: CWE-416

Description

Win32k Elevation of Privilege Vulnerability

Affected products

• Microsoft Windows 10 Version 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: 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 version 21H2: all versions
• Microsoft Windows 11 21H2: before 10.0.22000.258 — fixed in 10.0.22000.258
• Microsoft Windows 7: all versions
• Microsoft Windows 8.1: all versions
• Microsoft Windows RT 8.1: all versions
• Microsoft Windows Server 2004: before 10.0.19041.1288 — fixed in 10.0.19041.1288
• Microsoft Windows Server 2008: r2-sp1
• Microsoft Windows Server 2012: r2
• 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
• Microsoft Windows 10 Version 1507: from 10.0.0 before 10.0.10240.19086 — fixed in 10.0.10240.19086
• Microsoft Windows 10 1607: from 10.0.0 before 10.0.14393.4704 — fixed in 10.0.14393.4704
• Microsoft Windows 10: from 10.0.0 before 10.0.17763.2237 — fixed in 10.0.17763.2237
• Microsoft Windows 10 1909: from 10.0.0 before 10.0.18363.1854 — fixed in 10.0.18363.1854
• Microsoft Windows 10 2004: from 10.0.0 before 10.0.19041.1288 — fixed in 10.0.19041.1288
• Microsoft Windows 10 20H2: from 10.0.0 before 10.0.19041.1288 — fixed in 10.0.19041.1288
• Microsoft Windows 10 21H1: from 10.0.0 before 10.0.19041.1288 — fixed in 10.0.19041.1288
• Microsoft Windows 11 21H2: from 10.0.0 before 10.0.22000.258 — fixed in 10.0.22000.258
• Microsoft Windows 7: from 6.1.0 before 6.1.7601.25740 — fixed in 6.1.7601.25740
• Microsoft Windows 7 Service Pack 1: from 6.1.0 before 6.1.7601.25740 — fixed in 6.1.7601.25740
• Microsoft Windows 8.1: from 6.3.0 before 6.3.9600.20144 — fixed in 6.3.9600.20144

How to fix

Upgrade to a fixed version: Microsoft Windows 10 Version 1507 10.0.10240.19086; Microsoft Windows 10 1607 10.0.14393.4704; Microsoft Windows 10 10.0.17763.2237; Microsoft Windows 10 1909 10.0.18363.1854; Microsoft Windows 10 2004 10.0.19041.1288; Microsoft Windows 10 20H2 10.0.19041.1288; Microsoft Windows 10 21H1 10.0.19041.1288; Microsoft Windows 11 21H2 10.0.22000.258; Microsoft Windows Server 2004 10.0.19041.1288; Microsoft Windows Server 2016 10.0.14393.4704; Microsoft Windows Server 2019 10.0.17763.2237; Microsoft Windows Server 2022 10.0.20348.288. Check the vendor advisory for mitigations.

References

• http://packetstormsecurity.com/files/164926/Win32k-NtGdiResetDC-Use-After-Free-Local-Privilege-Escalation.html
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40449
• http://packetstormsecurity.com/files/164926/Win32k-NtGdiResetDC-Use-After-Free-Local-Privilege-Escalation.html
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40449
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40449

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