CVE-2021-31955
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 · uneditedWindows Kernel Information Disclosure Vulnerability
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 Windows Kernel information disclosure vulnerability that allows an authenticated attacker to potentially read sensitive kernel memory contents. The vulnerability is in the Windows kernel component and could be used to gather information for further exploitation or to expose sensitive system data.
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< 10.0.17763.1999< 10.0.18363.1621< 10.0.19041.1052< 10.0.19042.1052< 10.0.19043.1052< 10.0.19041.1052< 10.0.17763.1999< 10.0.19042.1052CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:L/AC:L/PR:L/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 Windows major version and build numberRun 'winver' from command prompt or check 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to identify your Windows edition and full build number including the UBR (Update Build Revision)Affected if Your Windows version matches 10.x but the full build number (including UBR) is lower than the fixed version for your specific Windows 10 or Windows Server release
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Identify exact Windows 10 release versionRun 'reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion" /v DisplayVersion' to see if it shows 1809, 1909, 2004, 20H2, or 21H1, then check the UBR value with 'reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion" /v UBR'Affected if DisplayVersion shows an affected release (1809, 1909, 2004, 20H2, or 21H1) and the UBR value is below the fixed threshold for that release
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Check Windows Server version and buildFor Windows Server, run 'systeminfo' or check registry 'HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion' to identify if it is Server 2019, Server version 2004, or Server version 20H2, and note the full build numberAffected if Running Windows Server 2019, Server 2004, or Server 20H2 with a build number below the fixed version for that server release
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Verify kernel version alignmentConfirm the build number from 'winver' or 'systeminfo' matches the kernel version by checking 'ver' command output, ensuring the OS build is consistent across all sourcesAffected if The OS build number displayed is inconsistent or shows a version below the fixed thresholds listed for any of the affected products
You are affected if your Windows 10 or Windows Server installation matches any of the listed versions (1809, 1909, 2004, 20H2, 21H1, Server 2019, Server 2004, Server 20H2) and your full build number including UBR is lower than the fixed version for that specific release.
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 · scoped10.0.17763.199910.0.18363.162110.0.19041.1052
Apply the Microsoft security updates released for June 2021 that address this kernel vulnerability. Prioritize patching for systems exposed to the internet or handling sensitive data.
Windows 10 1809: 10.0.17763.1999 | Windows 10 1909: 10.0.18363.1621 | Windows 10 2004: 10.0.19041.1052 | Windows 10 20h2: 10.0.19042.1052 | Windows 10 21h1: 10.0.19043.1052 | Windows Server 2019: 10.0.17763.1999 | Windows Server 20h2: 10.0.19042.1052
- Open Windows Settings and navigate to Update & Security > Windows Update
- Click 'Check for updates' to install the latest security updates
- Alternatively, manually download and install the appropriate KB5003173 (or later) cumulative update for your Windows version from the Microsoft Update Catalog
- Restart the system after installing the update
- Verify the installation by checking Windows Update history for the installed security update
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing12.0 h
- Review / QA6.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,192.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-31955 — 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-2021-31955 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