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Windows Server 2012Operating system · Microsoft

CVE-2026-26154

HIGH · 7.5 CVSS v3.1 Published 2026-04-14
Fix available
A fix is available. Upgrade to 10.0.14393.9060 / 10.0.17763.8644 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

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

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

Improper input validation vulnerability in Windows Server Update Service (WSUS) allows unauthenticated remote attackers to perform data tampering over the network. The vulnerability stems from insufficient validation of user-supplied input within the WSUS component, potentially allowing injection or manipulation of update metadata.

MitigationApply Microsoft security updates for CVE-2026-26154 to address the input validation weakness in WSUS. Verify WSUS functionality and monitor for signs of tampering post-patch.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Windows Server 2012Operating system
Affected:all versions= r2
Windows Server 2016Operating system
Affected:< 10.0.14393.9060
Windows Server 2019Operating system
Affected:< 10.0.17763.8644
Windows Server 2022Operating system
Affected:< 10.0.20348.5020
Windows Server 2022 23h2Operating system
Affected:< 10.0.25398.2274
Windows Server 2025Operating system
Affected:< 10.0.26100.32690

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Windows Server version build number
    Run 'winver' or 'systeminfo | findstr /B /C:"OS Version"' to obtain the full build number (e.g., 10.0.14393.xxxx)
    Affected if The build number falls below the safe threshold for your Server version: 2016 (< 10.0.14393.9060), 2019 (< 10.0.17763.8644), 2022 (< 10.0.20348.5020), 2022 23h2 (< 10.0.25398.2274), 2025 (< 10.0.26100.32690). Server 2012/R2 has no threshold and is fully affected.
  2. Verify WSUS server role is installed
    Run 'Get-WindowsFeature -Name UpdateServices' in PowerShell or check 'Server Manager > Add Roles and Features' for the WSUS role under 'Windows Server Update Services'
    Affected if The WSUS role is installed and the server falls within an affected version range from step 1
  3. Confirm WSUS service is running
    Run 'Get-Service -Name WsusService' or check Services.msc for 'Windows Server Update Service' status
    Affected if The WSUS service is started (Running) on a vulnerable version
  4. Check WSUS website binding in IIS
    Open IIS Manager, expand Sites, and verify 'WSUS Administration' website exists and is running on port 8530 or 443
    Affected if The WSUS Administration site is present and active on a vulnerable server version

A server is affected if it runs a vulnerable Windows Server version (2012/R2, or 2016/2019/2022/2025 below the build thresholds) AND has the WSUS server role installed and operational.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 10.0.14393.9060 / 10.0.17763.8644 / 10.0.20348.5020 or later
Fixed in 10.0.14393.906010.0.17763.864410.0.20348.5020
Interim mitigation

Apply Microsoft security updates for CVE-2026-26154 to address the input validation weakness in WSUS. Verify WSUS functionality and monitor for signs of tampering post-patch.

Recommended fix High confidence

Windows Server 2016: build 10.0.14393.9060+ | Windows Server 2019: build 10.0.17763.8644+ | Windows Server 2022: build 10.0.20348.5020+ | Windows Server 2022 23h2: build 10.0.25398.2274+ | Windows Server 2025: build 10.0.26100.32690+

  1. 1. Identify the current Windows Server version by running 'winver' or 'systeminfo' in Command Prompt
  2. 2. Determine which Windows Server version family your server is running (2012, 2016, 2019, 2022, or 2025)
  3. 3. For Windows Server 2016: Apply KB6013866 (or subsequent update) to reach build 10.0.14393.9060 or later
  4. 4. For Windows Server 2019: Apply KB6013866 (or subsequent update) to reach build 10.0.17763.8644 or later
  5. 5. For Windows Server 2022: Apply KB6013866 (or subsequent update) to reach build 10.0.20348.5020 or later
  6. 6. For Windows Server 2022 23h2: Apply KB6013866 (or subsequent update) to reach build 10.0.25398.2274 or later
  7. 7. For Windows Server 2025: Apply KB6013866 (or subsequent update) to reach build 10.0.26100.32690 or later
  8. 8. Restart the server after applying the update
Caveat Windows Server 2012 has no fix available as it is end-of-life; consider migrating to a supported version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Windows Server 2012 Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,900
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-26154 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data