CVE-2026-20877
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 · uneditedUse after free in Windows Management Services allows an authorized attacker to elevate privileges locally.
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 · moderate confidenceA use-after-free vulnerability in Windows Management Services allows a locally authorized attacker to execute code with elevated privileges. The flaw involves improper memory handling where a pointer is accessed after being freed, leading to potential arbitrary code execution in kernel or SYSTEM context.
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< 10.0.17763.8276< 10.0.19044.6809< 10.0.19045.6809< 10.0.22631.6491< 10.0.26100.7623< 10.0.26200.7623< 10.0.17763.8276< 10.0.20348.4648CVSS 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
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/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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Check Windows version and build numberRun 'winver' from Run dialog or execute 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' in Command Prompt. Alternatively, query the registry with 'reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion" /v BuildLabEx'Affected if The installed version falls below any of these thresholds: 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 < 10.0.26200.7623, Server 2019 < 10.0.17763.8276,
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Verify Windows Management Services statusOpen Services.msc and locate Windows Management Instrumentation (WMI) service, or run 'sc query winmgmt' in Command Prompt to check if the service is runningAffected if The Windows Management Instrumentation service is running and the OS version is below the patched build numbers listed above
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Check for WinRM service exposureRun 'sc query WinRM' in Command Prompt to determine if Windows Remote Management service is enabled, or check via Services.mscAffected if WinRM service is enabled and the OS version is vulnerable according to the version thresholds
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Review recent security event logs for management service anomaliesOpen Event Viewer, navigate to Windows Logs > System, and filter for Event ID 7036 (service control) related to WinMgmt or WMI provider host processes within recent daysAffected if Unexpected service restarts or crashes are logged for WMI-related services on an unpatched system
A user is affected if their installed Windows version is below the specified build numbers AND Windows Management Services (WMI/WinRM) are enabled on the system.
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 · scoped10.0.17763.827610.0.19044.680910.0.19045.6809
Apply Microsoft security updates for Windows Management Services when available; restrict local access to trusted users; monitor for indicators of compromise such as unexpected processes spawning from management service contexts.
Install the Microsoft security update for CVE-2026-20877; fixed builds are: 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 (10.0.26200.7623), Server 2019 (1
- Identify the current Windows build version by running 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"'
- Determine which affected product category your system falls into (Windows 10 version 1809, 21h2, 22h2, Windows 11 23h2, 24h2, 25h2, Server 2019, or Server 2022)
- Open Settings > Windows Update and check for updates, or visit the Microsoft Update Catalog at https://catalog.update.microsoft.com/
- Search for the Microsoft security update corresponding to this CVE (CVE-2026-20877) for your specific Windows version
- Download and install the appropriate security update that brings your build to the fixed version or higher
- Restart the system after installation
- Verify the update was successful by checking the installed updates list or running 'winver' to confirm the build number matches or exceeds the fixed version
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation8.0 h
- Implementation24.0 h
- Testing16.0 h
- Review / QA8.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20877 — 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-2026-20877 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
- No spam, self-promotion, credentials, or personal data