CVE-2026-20821
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 · uneditedExposure of sensitive information to an unauthorized actor in Windows Remote Procedure Call allows an unauthorized attacker to disclose information 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 · moderate confidenceThis is a local information disclosure vulnerability in Windows Remote Procedure Call (RPC). An unauthorized attacker can exploit this to disclose sensitive information locally, though the specific sensitive data or RPC function involved is not detailed in the available description.
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
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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 installed Windows versionOpen Command Prompt and run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to see the exact Windows build numberAffected if The version shown is below the fixed build number for your Windows release (e.g., below 10.0.14393.8783 for Windows 10 1607, below 10.0.17763.8276 for Windows 10 1809, etc.)
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Identify Windows release versionRun 'winver' to see if you are on 1607, 1809, 21h2, 22h2 or check systeminfo for the exact build. For Windows 11, check if you are on 23h2, 24h2, or 25h2 by running 'winver'Affected if Your system matches one of the affected Windows 10 or 11 releases listed in the CVE and the build number is below the fixed version
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Verify RPC service is runningOpen Services (services.msc) and locate 'Remote Procedure Call (RPC)' and 'Remote Procedure Call (RPC) Locator' services, or run 'sc query rpcss' in Command PromptAffected if The RPC services are running (this is default on Windows, making the potential disclosure possible)
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Check for untrusted local usersRun 'net user' in Command Prompt to list local user accounts, then assess whether any accounts belong to untrusted or non-administrative usersAffected if There are local user accounts beyond the administrator that are not fully trusted, as the vulnerability allows local unauthorized users to potentially access sensitive information
You are affected if your Windows version matches any of the listed releases and is below the specified build numbers, and your system has local user accounts who could potentially exploit the RPC information disclosure.
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 available Microsoft security updates for Windows RPC when released. Until then, restrict local access to trusted users only and monitor for suspicious RPC activity.
Upgrade to 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 lat
- Identify the current Windows version and build number by running 'winver' or 'systeminfo'
- For Windows 10: Navigate to Settings > Windows Update and check for updates, or manually download the cumulative update matching your version from the Microsoft Update Catalog
- For Windows 11: Navigate to Settings > Windows Update and check for updates
- Verify the installation succeeded by running 'winver' and confirming the build number meets or exceeds the fixed version for your Windows release
- For Windows Server 2008/R2: Since these versions are end-of-life and receive no further security updates, migrate to a supported Windows Server version (2019, 2022, or 2025)
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20821 — 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-2026-20821 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