---
id: CVE-2026-26154
title: Windows Server Update Service (WSUS) Tampering Vulnerability
summary: >-
  Improper input validation in Windows Server Update Service allows an
  unauthorized attacker to perform tampering over a network.
severity: high
cvss: 7.5
cvssVector: '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'
cvssSource: cna
cwe:
  - CWE-20
vendor: Microsoft
product: Windows Server 2012
affected:
  - windows_server_2012 >= 6.2.9200.0 < 6.2.9200.26026
  - windows_server_2012_server_core_installation >= 6.2.9200.0 < 6.2.9200.26026
  - windows_server_2012_r2 >= 6.3.9600.0 < 6.3.9600.23132
  - >-
    windows_server_2012_r2_server_core_installation >= 6.3.9600.0 <
    6.3.9600.23132
  - windows_server_2016 >= 10.0.14393.0 < 10.0.14393.9060
  - >-
    windows_server_2016_server_core_installation >= 10.0.14393.0 <
    10.0.14393.9060
  - windows_server_2019 >= 10.0.17763.0 < 10.0.17763.8644
  - >-
    windows_server_2019_server_core_installation >= 10.0.17763.0 <
    10.0.17763.8644
  - windows_server_2022 >= 10.0.20348.0 < 10.0.20348.5020
  - >-
    windows_server_2022_23h2_edition_server_core_installation >= 10.0.25398.0 <
    10.0.25398.2274
  - windows_server_2025 >= 10.0.26100.0 < 10.0.26100.32690
  - >-
    windows_server_2025_server_core_installation >= 10.0.26100.0 <
    10.0.26100.32690
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-04-14T17:59:13.916318Z'
published: '2026-04-14'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T17:24:55.094Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-26154'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26154'
    label: Windows Server Update Service (WSUS) Tampering Vulnerability
tags:
  - cve.org
epss: 0.01232
epssPercentile: 0.67705
ingestedAt: '2026-09-25T18:14:20.461Z'
---

## Overview

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

## Affected

- `windows_server_2012 >= 6.2.9200.0 < 6.2.9200.26026`
- `windows_server_2012_server_core_installation >= 6.2.9200.0 < 6.2.9200.26026`
- `windows_server_2012_r2 >= 6.3.9600.0 < 6.3.9600.23132`
- `windows_server_2012_r2_server_core_installation >= 6.3.9600.0 < 6.3.9600.23132`
- `windows_server_2016 >= 10.0.14393.0 < 10.0.14393.9060`
- `windows_server_2016_server_core_installation >= 10.0.14393.0 < 10.0.14393.9060`
- `windows_server_2019 >= 10.0.17763.0 < 10.0.17763.8644`
- `windows_server_2019_server_core_installation >= 10.0.17763.0 < 10.0.17763.8644`
- `windows_server_2022 >= 10.0.20348.0 < 10.0.20348.5020`
- `windows_server_2022_23h2_edition_server_core_installation >= 10.0.25398.0 < 10.0.25398.2274`
- `windows_server_2025 >= 10.0.26100.0 < 10.0.26100.32690`
- `windows_server_2025_server_core_installation >= 10.0.26100.0 < 10.0.26100.32690`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.