CVE-2025-21204
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 · uneditedImproper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.
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 confidenceThis is a link following (symlink race) vulnerability in the Windows Update Stack where the software fails to properly resolve symbolic or hard links before accessing files. A local attacker with authorized access can exploit this race condition to manipulate file paths and elevate privileges to higher integrity levels.
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< 10.0.10240.20978< 10.0.14393.7969< 10.0.17763.7136< 10.0.19044.5737< 10.0.19045.5737< 10.0.22621.5189< 10.0.22631.5189< 10.0.26100.3775CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 checksWork through these to decide whether this CVE applies to you.
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Check installed Windows versionRun 'winver' from the Start menu search or execute 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' in Command Prompt to obtain the exact Windows build numberAffected if The build number falls below any of these thresholds: Windows 10 1507 < 10.0.10240.20978, Windows 10 1607 < 10.0.14393.7969, Windows 10 1809 < 10.0.17763.7136, Windows 10 21h2 < 10.0.19044.5737, Windows 10 22h2 < 10.0.19045.5737, Windows 11 22h2 < 10.0.22621.5189, Windows 11 23h2 < 10.0.22631.5189,
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Identify Windows 10 releaseRun 'winver' and note the specific Windows 10 release (such as 1507, 1607, 1809, 21h2, or 22h2) shown in the dialogAffected if Your Windows 10 release matches one of the affected versions listed above and its build is below the corresponding threshold
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Check if CVE-2025-21204 patch is installedOpen Settings > Windows Update > View update history, or run 'wmic qfe list' in Command Prompt to list installed hotfixes. Look for any security update installed after the CVE release dateAffected if No security update addressing CVE-2025-21204 appears in the installed updates and your Windows version is within the affected range
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Verify Windows Update component is in useConfirm that the Windows Update service (wuauserv) is present and configurable on the system. This is the component containing the vulnerable symlink handling codeAffected if The Windows Update service exists and operates on a Windows version below the fixed build numbers
You are affected if your installed Windows version falls below any of the specified build numbers and the CVE-2025-21204 security update has not been applied.
Generated from the published advisory. Verify against your own configuration.
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 · scoped10.0.10240.2097810.0.14393.796910.0.17763.7136
Apply the Microsoft security update for CVE-2025-21204 through Windows Update or manual patch deployment. In enterprise environments, test the update in a staging environment before broad deployment to ensure compatibility with existing Windows Update infrastructure.
Windows 10 1507: build 10.0.10240.20978 | Windows 10 1607: build 10.0.14393.7969 | Windows 10 1809: build 10.0.17763.7136 | Windows 10 21h2: build 10.0.19044.5737 | Windows 10 22h2: build 10.0.19045.5737 | Windows 11 22h2: build 10.0.22621.5189 | Windows 11 23h2: build 10.0.22631.5189 | Windows 11 2
- Identify the current Windows version and build by running 'winver' or 'systeminfo' in Command Prompt
- Determine which Windows 10/11 version and feature update you are running (e.g., 1507, 1607, 1809, 21h2, 22h2, or Windows 11 22h2/23h2/24h2)
- Open Windows Update by going to Settings > Update & Security > Windows Update
- Click 'Check for updates' to receive the appropriate security update for your specific build
- Alternatively, manually download and install the corresponding Security Update from the Microsoft Update Catalog for your Windows version: For Windows 10 1507 (build 10.0.10240), install KB5055527; for Windows 10 1607 (build 10.0.14393), install KB5055528; for Windows 10 1809 (build 10.0.17763), install KB5055529; for Windows 10 21h2 (build 10.0.19044), install KB5055531; for Windows 10 22h2 (buil
- Restart the computer after the update is installed
- Verify the update installed successfully by checking Windows Update history or running 'winver' to confirm the build number matches or exceeds the fixed version for your release
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-21204 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-21204 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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