dbcve.org
Windows 10 1607Operating system · Microsoft

CVE-2026-26173

HIGH · 7.0 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 →
72/100
Remediation priority · Elevated
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
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Ancillary Function Driver for WinSock 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 confidence

A race condition exists in the Windows Ancillary Function Driver (AFD.sys) for WinSock where improper synchronization of shared resources allows a local authenticated attacker to manipulate timing and elevate privileges to SYSTEM level.

MitigationApply the Microsoft security update for CVE-2026-26173 to all affected Windows systems. Prioritize workstations and servers with exposed attack surfaces.

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:< 10.0.14393.9060
Windows 10 1809Operating system
Affected:< 10.0.17763.8644
Windows 10 21h2Operating system
Affected:< 10.0.19044.7184
Windows 10 22h2Operating system
Affected:< 10.0.19045.7184
Windows 11 23h2Operating system
Affected:< 10.0.22631.6936
Windows 11 24h2Operating system
Affected:< 10.0.26100.8246
Windows 11 25h2Operating system
Affected:< 10.0.26200.8246
Windows 11 26h1Operating system
Affected:< 10.0.28000.1836

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
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/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 version
    Run 'winver' or 'systeminfo | findstr /B /C:"OS Version"' to obtain the full build number (e.g., 10.0.19045.7184)
    Affected if The build number is lower than any of the affected thresholds: 14393.9060 (1607), 17763.8644 (1809), 19044.7184 (21h2), 19045.7184 (22h2), 22631.6936 (23h2), 26100.8246 (24h2), 26200.8246 (25h2), or 28000.1836 (26h1)
  2. Verify AFD.sys file version
    Open File Explorer to C:\Windows\System32\drivers\afd.sys, right-click and select Properties, then view the Details tab to see the File Version
    Affected if The AFD.sys version is lower than the version bundled with the patched build for your Windows release (this corresponds to the same build thresholds listed above)
  3. Confirm AFD.sys is loaded
    Run 'sc query afd' or 'driverquery /v | findstr afd' to verify the AFD (Ancillary Function Driver) service or driver is present and running
    Affected if The driver is loaded and the Windows build version falls within the affected range, indicating exposure to the race condition vulnerability
  4. Audit local user privileges
    Run 'whoami /priv' or 'net user [username]' to review current user privileges; the vulnerability requires a local authenticated user to exploit the race condition
    Affected if A local authenticated user account exists on the system and the Windows build is in the affected range, meaning the privilege escalation path is present

You are affected if your Windows build number is below the threshold for your specific Windows version (10 or 11, release channel) and AFD.sys is loaded, since a local authenticated attacker could exploit the race condition to gain SYSTEM privileges.

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 / 10.0.19044.7184 or later
Fixed in 10.0.14393.906010.0.17763.864410.0.19044.7184
Interim mitigation

Apply the Microsoft security update for CVE-2026-26173 to all affected Windows systems. Prioritize workstations and servers with exposed attack surfaces.

Recommended fix High confidence

Windows 10 1607: 10.0.14393.9060 or later | Windows 10 1809: 10.0.17763.8644 or later | Windows 10 21h2: 10.0.19044.7184 or later | Windows 10 22h2: 10.0.19045.7184 or later | Windows 11 23h2: 10.0.22631.6936 or later | Windows 11 24h2: 10.0.26100.8246 or later | Windows 11 25h2: 10.0.26200.8246 or

  1. Identify the current Windows version by running 'winver' or checking System Properties
  2. Determine if the current build number is below the fixed version for your Windows edition
  3. Open Windows Settings > Windows Update
  4. Click 'Check for updates' to download and install the latest cumulative security updates from Microsoft
  5. Restart the system when prompted to complete the update installation
  6. Verify the update was installed by checking the build number matches or exceeds the fixed version for your Windows edition

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

Fix this in Windows 10 1607 Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2026-26173 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