CVE-2026-20869
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 Local Session Manager (LSM) allows an authorized attacker to elevate privileges locally.
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 · high confidenceA race condition vulnerability exists in Windows Local Session Manager (LSM) due to improper synchronization when accessing shared resources. An authorized local attacker can exploit this timing vulnerability to elevate their privileges from a standard user to higher system privileges.
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
- 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 checksWork through these to decide whether this CVE applies to you.
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Identify Windows version and build numberRun 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to retrieve the exact Windows version and build numberAffected if The build number is lower than the affected versions: 14393.8783 (Win10 1607), 17763.8276 (Win10 1809), 19044.6809 (Win10 21h2/22h2), 22631.6491 (Win11 23h2), 26100.7623 (Win11 24h2), 26200.7623 (Win11 25h2), or any Windows Server 2008/R2 build
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Confirm Windows 10/11 edition and branchRun 'winver' to verify the specific Windows 10 release (1607, 1809, 21h2, 22h2) or Windows 11 version (23h2, 24h2, 25h2) because version ranges differ per releaseAffected if The detected Windows 10/11 release matches an affected version range and its build is below the corresponding fixed build
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Verify Local Session Manager service statusRun 'sc query LSM' or check Services.msc for the 'Local Session Manager' service to confirm it is runningAffected if The LSM service is present and running on the system (required for the vulnerability to be exploitable)
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Check Windows Server version if applicableRun 'systeminfo' or 'winver' on Windows Server systems to identify the exact build versionAffected if The system is Windows Server 2008 or Windows Server 2008 R2 (all versions affected per the CVE)
A system is affected if it runs any Windows 10 or Windows 11 version with a build number below the fixed thresholds, or any version of Windows Server 2008/R2, and has the Local Session Manager service enabled.
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 this vulnerability through Windows Update or enterprise patch management systems. Verify the patch is successfully deployed and test for any compatibility issues.
Windows 10 1607: Build 10.0.14393.8783 or later | Windows 10 1809: Build 10.0.17763.8276 or later | Windows 10 21h2: Build 10.0.19044.6809 or later | Windows 10 22h2: Build 10.0.19045.6809 or later | Windows 11 23h2: Build 10.0.22631.6491 or later | Windows 11 24h2: Build 10.0.26100.7623 or later |
- Open Windows Settings and navigate to Update & Security > Windows Update
- Click 'Check for updates' to download and install the latest security updates
- Alternatively, manually download and install the appropriate cumulative update for your Windows version from the Microsoft Update Catalog
- Restart the system after updates are installed
- Verify the build version matches or exceeds the fixed version for your Windows release
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 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 $4,096.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20869 — 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-2026-20869 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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- 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
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