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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 4 Mar 2025.
Windows 10 1607Operating system · Microsoft

CVE-2025-21418

HIGH · 7.8 CVSS v3.1 Published 2025-02-11
Fix available
A fix is available. Upgrade to 10.0.10240.20915 / 10.0.17763.6893 or later.
See remediation →
96/100
Remediation priority · Urgent
In the wild Zero-click Patch available

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
Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

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

This is a local Elevation of Privilege vulnerability in the Windows Ancillary Function Driver for WinSock (Afd.sys), a kernel-mode driver that supports Windows Sockets (Winsock) API. The vulnerability allows a local attacker to gain elevated privileges on the affected system.

MitigationApply the security updates provided by Microsoft for this vulnerability through Windows Update or Microsoft Update Catalog. Until patches are available, limit local access to trusted users and monitor for suspicious process activity.

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 10 1607Operating system
Affected:< 10.0.10240.20915
Windows 10 1809Operating system
Affected:< 10.0.17763.6893
Windows 10 21h2Operating system
Affected:< 10.0.19044.5487
Windows 10 22h2Operating system
Affected:< 10.0.19045.5487
Windows 11 22h2Operating system
Affected:< 10.0.22621.4890
Windows 11 23h2Operating system
Affected:< 10.0.22631.4890
Windows 11 24h2Operating system
Affected:< 10.0.26100.3107
Windows Server 2008Operating system
Affected:all versions= r2

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
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 checks

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

  1. Check Windows build number
    Run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to identify the exact Windows build
    Affected if The build number falls below the fixed versions: 10240.20915, 17763.6893, 19044.5487, 19045.5487, 22621.4890, 22631.4890, or 26100.3107 depending on your Windows release
  2. Identify Windows release version
    Run 'winver' to determine if you are on Windows 10 1607, 1809, 21h2, 22h2, or Windows 11 22h2, 23h2, 24h2
    Affected if You are on any of these releases and the corresponding build is below the fixed version for that release
  3. Check AFD driver file version
    Navigate to C:\Windows\System32\drivers\afd.sys, right-click Properties, and view the File Version, or run 'powershell "(Get-Item C:\Windows\System32\drivers\afd.sys).VersionInfo.FileVersion"'
    Affected if The file version is older than the patched version for your specific Windows release (compare against the build numbers above)
  4. Verify Windows Update patch status
    Open Settings > Windows Update > Update History and look for security updates with KB number relating to CVE-2025-21418, or run 'powershell "Get-HotFix | Where-Object {$_.Description -like '*Security*'} | Sort-Object InstalledOn -Descending | Select-Object -First 10"'
    Affected if No security update addressing CVE-2025-21418 appears in the installed updates history

You are affected if your Windows build number is below the fixed version for your specific Windows release and no corresponding security patch for CVE-2025-21418 is installed.

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 10.0.10240.20915 / 10.0.17763.6893 / 10.0.19044.5487 or later
Fixed in 10.0.10240.2091510.0.17763.689310.0.19044.5487
Vendor patch msrc.microsoft.com →
Interim mitigation

Apply the security updates provided by Microsoft for this vulnerability through Windows Update or Microsoft Update Catalog. Until patches are available, limit local access to trusted users and monitor for suspicious process activity.

Recommended fix High confidence

Microsoft security update KB (apply the relevant monthly security patch for February 2025 or later that addresses CVE-2025-21418)

  1. Identify the current Windows version by running 'winver' or 'systeminfo' in Command Prompt
  2. Determine which version band applies (e.g., Windows 10 22h2, Windows 11 23h2, etc.)
  3. Apply the appropriate Microsoft security update for CVE-2025-21418 via Windows Update, or manually download and install the specific KB from the Microsoft Update Catalog
  4. Restart the system when prompted to complete the installation
  5. Verify the installed version meets or exceeds the fixed version for your Windows release (e.g., Windows 10 22h2 should be >= 10.0.19045.5487)
  6. Confirm the vulnerability is remediated by checking that the security update appears in 'View update history'
Caveat Standard Windows update apply risk - ensure backups and compatibility testing for mission-critical systems before deploying

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

Fix this in Windows 10 1607 Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing8.0 h
  • Review / QA4.0 h
18.0 hours of engineering $3,080
Get it fixed fast

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,928.

Scan for this in your stack

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dbcve dependency scanner

Check whether your project pulls in CVE-2025-21418 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

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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-2025-21418 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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