CVE-2026-20919
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 · uneditedConcurrent execution using shared resource with improper synchronization ('race condition') in Windows SMB Server allows an authorized attacker to elevate privileges over a network.
In the news
Third-party coverage- Microsoft CVE Summary - Bleeping Computer
- Microsoft January 2026 Patch Tuesday fixes 3 zero-days, 114 flaws
Surfaced from public web coverage — external links open in a new tab.
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 · low confidenceThis is a race condition vulnerability in Windows SMB Server where concurrent execution with improper synchronization allows an authenticated attacker to elevate privileges over a network. The vulnerability stems from improper handling of shared resources during simultaneous operations.
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< 10.0.14393.8783< 10.0.17763.8276< 10.0.19044.6809< 10.0.19045.6809< 10.0.22631.6491< 10.0.26100.7623< 10.0.26200.7623all versions= r2CVSS 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
- High
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/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 checksWork through these to decide whether this CVE applies to you.
-
Determine Windows version and build numberRun 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to get the exact build numberAffected if The build number falls below any of these thresholds: 14393.8783 (1607), 17763.8276 (1809), 19044.6809 (21h2), 19045.6809 (22h2), 22631.6491 (23h2), 26100.7623 (24h2), 26200.7623 (25h2)
-
Confirm SMB Server is enabledRun 'Get-SmbServerConfiguration' in PowerShell or check Services for 'Server' service status. Also run 'Get-WindowsOptionalFeature -Online -FeatureName SMB1Protocol' to check SMBv1 statusAffected if SMB Server (SMBv1, SMBv2, or SMBv3) is enabled and running on the target system
-
Verify SMB service is listening on the networkRun 'netstat -an | findstr "445"' or 'Test-NetConnection -ComputerName localhost -Port 445' to confirm SMB is bound to network interfacesAffected if TCP port 445 is listening and SMB is exposed over the network
-
Check authentication method in useReview SMB configuration with 'Get-SmbServerConfiguration | Select-Object *' and check if domain or local accounts are used for SMB accessAffected if The system allows authenticated network connections to SMB (this is required for the attacker to be authenticated)
You are affected if your Windows build number is below the fixed versions AND SMB Server is enabled and accessible for authenticated network connections.
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 · scoped10.0.14393.878310.0.17763.827610.0.19044.6809
Apply Microsoft security patches for Windows SMB Server when available, implement network segmentation to limit SMB exposure, and follow least privilege principles for user accounts.
Windows Cumulative Security Update (specific build numbers per version listed in steps)
- Identify the Windows version and build number by running 'winver' or 'systeminfo' on the affected system
- Open Settings > Windows Update and check for available updates
- Install all cumulative security updates for your Windows version
- For Windows Server 2012/2012 R2, apply the relevant cumulative update from Microsoft Update Catalog
- Restart the system after applying updates
- Verify the installed build matches or exceeds the fixed version: Windows 10 1607 should be 10.0.14393.8783 or later; Windows 10 1809 should be 10.0.17763.8276 or later; Windows 10 21h2 should be 10.0.19044.6809 or later; Windows 10 22h2 should be 10.0.19045.6809 or later; Windows 11 23h2 should be 10.0.22631.6491 or later; Windows 11 24h2 should be 10.0.26100.7623 or later; Windows 11 25h2 should
- For Windows Server 2012/2012 R2 which has no fixed version listed, consider upgrading to a supported Windows Server version as these are end-of-life
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,888.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20919 — 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-2026-20919 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
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.
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.
- 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