CVE-2021-1676
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 NT Lan Manager Datagram Receiver Driver 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 an information disclosure vulnerability in the Windows NT Lan Manager Datagram Receiver Driver (likely a network driver component handling NetBIOS datagram traffic). The flaw allows a local attacker to read sensitive information from kernel memory due to improper bounds checking or memory access controls in the driver.
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 versionsall versionsall versions= r2all versions= r2all versions= 20h2= 1909= 2004all versionsCVSS 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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Identify Windows version and build numberRun 'winver' from the command prompt, or use 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to retrieve the exact version and build. On PowerShell, run '[System.Environment]::OSVersion.Version' or 'Get-ComputerInfo | Select-Object WindowsProductName, WindowsVersion, OsHardwareAbstractionLayer'Affected if The version falls within the listed affected products: Windows 10 (any version, or specifically 20h2, 1607, 1803, 1809, 1909, 2004), Windows 7 (all versions), Windows 8.1 (all versions), Windows Rt 8.1 (all versions), Windows Server 2008 (all versions or R2), Windows Server 2012 (all versions or R2)
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Verify the security update is installedOpen Control Panel > Programs and Features > View installed updates, or run 'Get-HotFix' in PowerShell to list installed hotfixes. Search for the CVE-2021-1676 security update (typically delivered via a Windows Update or monthly security rollup)Affected if The security update for CVE-2021-1676 is NOT installed on the system (the system remains vulnerable)
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Confirm driver presence and statusCheck that the NT Lan Manager Datagram Receiver Driver (netbt.sys) is present on the system by examining the driver file at %SystemRoot%\System32\drivers\netbt.sys, or query via 'driverquery /v | findstr netbt'Affected if The driver exists and the system is unpatched (the vulnerability resides in this driver component)
A system is affected if it runs any of the listed Windows versions and the CVE-2021-1676 security update has not been installed, leaving the netbt.sys driver vulnerable to kernel memory 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.
From vendor dataApply the Microsoft security update for CVE-2021-1676 via Windows Update or enterprise patch management systems; verify that affected Windows systems are fully patched.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 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 $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-1676 — 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-2021-1676 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