CVE-2021-1637
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 DNS Query 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 confidenceWindows DNS Query Information Disclosure Vulnerability - an information disclosure flaw in Windows DNS service that allows a locally authenticated attacker to potentially access DNS query information. CVSS 5.5 indicates low confidentiality impact with no integrity or availability impact.
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 dataall versions= 20h2= 1607= 1803= 1809= 1909= 2004all versionsall versions= r2all versions= 20h2= 1909= 2004CVSS 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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Verify DNS Server role is installedRun 'Get-WindowsFeature -Name DNS' in PowerShell or check 'DNS Server' in Server Manager under Roles. On client Windows, check if the DNS Server service exists in Services (services.msc).Affected if DNS Server role is installed and running - this is required for the vulnerability to be exploitable
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Confirm Windows version is affectedRun 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to identify the exact Windows version and build number.Affected if Windows 10 (20h2, 1607, 1803, 1809, 1909, 2004), Windows 8.1 all versions, Windows RT 8.1, Windows Server 2012 R2, or Windows Server 2016 (20h2, 1909, 2004) is detected
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Check if DNS Server service is runningRun 'Get-Service -Name DNS' in PowerShell or check the DNS Server service status in services.msc.Affected if DNS Server service is running - an attacker needs local authentication and this service must be active to exploit the flaw
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Verify security update installationRun 'Get-HotFix | Where-Object {$_.Description -eq "Security Update"} | Select-Object HotFixID, InstalledOn' and check if KB5001 is installed, or search for the CVE-2021-1637 specific patch in Windows Update history.Affected if The specific security update for CVE-2021-1637 is NOT installed - this indicates the system is vulnerable
A system is affected if it runs an affected Windows version, has the DNS Server role installed and running, and is missing the CVE-2021-1637 security update.
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.
From vendor dataApply the relevant Microsoft security update for CVE-2021-1637 to affected Windows systems. If immediate patching is not possible, consider network segmentation and limiting local privileged access as compensating controls.
- 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-2021-1637 — 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-2021-1637 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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