CVE-2026-20875
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 · uneditedNull pointer dereference in Windows Local Security Authority Subsystem Service (LSASS) allows an unauthorized attacker to deny service over a network.
In the news
Third-party coverage- Microsoft January 2026 Patch Tuesday fixes 3 zero-days, 114 flaws
- Microsoft CVE Summary - Bleeping Computer
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 confidenceA null pointer dereference vulnerability exists in the Windows Local Security Authority Subsystem Service (LSASS), a critical Windows security component responsible for enforcing security policy. An unauthenticated remote attacker can trigger the null pointer dereference, causing LSASS to crash and resulting in a denial of service across the system.
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
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 Windows version against affected rangesRun 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to obtain the installed Windows version and build numberAffected if The installed version and build number fall below any of these thresholds: 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
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Confirm LSASS process is runningOpen Task Manager, go to the Details tab, and verify lsass.exe is present and running; alternatively run 'tasklist | findstr lsass.exe'Affected if lsass.exe is not running or has recently crashed (indicating possible exploitation attempt)
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Check for LSASS crash eventsOpen Event Viewer, navigate to Windows Logs > Application and System, and filter for Event ID 1000 (Application Error) or Event ID 1001 (Windows Error Reporting) where the faulting module is lsass.exeAffected if Recent crash events for lsass.exe are found in the event logs
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Verify network exposure of LSASSRun 'netstat -ano | findstr "445 139"' and check for LISTENING state on ports 445 (SMB) and 139 (NetBIOS), as LSASS may be indirectly reachable through these services; also verify remote administration tools are not exposing LSASS to untrusted networksAffected if The system has open SMB or other network services that could allow remote triggering of the LSASS vulnerability from untrusted networks
The environment is affected if the Windows version falls below the patched build numbers AND LSASS network endpoints are accessible from untrusted networks, enabling remote denial of service.
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 Windows when available. Until a patch is released, monitor for suspicious activity targeting LSASS and implement network segmentation to limit exposure.
Upgrade to the following minimum fixed builds: 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 -> 10.0.26200.7
- Identify the current Windows build version by running 'winver' or 'systeminfo' in Command Prompt
- Navigate to Windows Update Settings and check for available security updates
- Apply the latest Cumulative Security Update for your Windows version from Microsoft Update Catalog
- For Windows Server 2008 (all versions, including R2): This OS is end-of-life and no longer receives security patches; migrate to a supported Windows Server version
- After applying updates, verify the new build version matches or exceeds the fixed build number for your product
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20875 — 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-2026-20875 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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