CVE-2026-20848
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 · moderate confidenceA race condition vulnerability exists in Windows SMB Server where concurrent execution operations share resources without proper synchronization. An authorized attacker with network access can exploit this timing vulnerability to elevate privileges beyond their assigned permissions.
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.
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Identify Windows versionRun 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to obtain the exact Windows build numberAffected if The build number falls within any of these vulnerable ranges: Windows 10 1607 < 10.0.14393.8783, Windows 10 1809 < 10.0.17763.8276, Windows 10 21h2 < 10.0.19044.6809, Windows 10 22h2 < 10.0.19045.6809, Windows 11 23h2 < 10.0.22631.6491, Windows 11 24h2 < 10.0.26100.7623, Windows 11 25h2 < 10.0.26200
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Verify SMB Server is enabledRun 'Get-SmbServerConfiguration' in PowerShell or check the 'Services' console for the 'Server' service statusAffected if The SMB Server service (srv2.sys or SMB service) is running and accepting connections; the vulnerability exists in the SMB Server component itself
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Confirm SMB network exposureRun 'Get-NetTCPConnection -State Listen | Where-Object {$_.LocalPort -eq 445}' or use 'netstat -ano | findstr :445' to check if SMB is listening on port 445Affected if Port 445 is open and listening, indicating SMB is exposed on the network for potential attacker access
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Review current user privilegesRun 'whoami /priv' or 'whoami /groups' to enumerate current user permissions and group membershipsAffected if The user has limited but authorized network access - the vulnerability allows privilege elevation beyond assigned permissions, so any non-privileged authenticated user could potentially exploit this
You are affected if your Windows build number is below the specified thresholds AND SMB Server is running and accessible on the network, allowing an authorized user to potentially elevate privileges through the race condition.
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 updates for SMB Server once available; restrict SMB access to authorized personnel and networks; monitor for unusual SMB traffic patterns.
Microsoft Windows Security Update (KB5055527 or subsequent KB) / Windows 10 version 22h2 (10.0.19045.6809+) / Windows 11 version 23h2 (10.0.22631.6491+)
- Identify the current Windows version by running 'winver' or 'systeminfo' in Command Prompt
- For Windows 10 1607 systems: upgrade to version 10.0.14393.8783 or later
- For Windows 10 1809 systems: upgrade to version 10.0.17763.8276 or later
- For Windows 10 21h2 systems: upgrade to version 10.0.19044.6809 or later
- For Windows 10 22h2 systems: upgrade to version 10.0.19045.6809 or later
- For Windows 11 23h2 systems: upgrade to version 10.0.22631.6491 or later
- For Windows 11 24h2 systems: upgrade to version 10.0.26100.7623 or later
- For Windows 11 25h2 systems: upgrade to version 10.0.26200.7623 or later
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20848 — 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-2026-20848 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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- Version or environment caveats, and links to real fixes
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