CVE-2021-36942
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 LSA Spoofing 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 · low confidenceThis is a spoofing vulnerability in Windows Local Security Authority (LSA), a critical Windows component responsible for authentication and policy enforcement. The vulnerability could allow an attacker to intercept or manipulate authentication processes, potentially gaining unauthorized access to systems or impersonating legitimate users.
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< 10.0.19041.1165all versions= r2all versions= r2< 10.0.14393.4583< 10.0.17763.2114< 10.0.19042.1165CVSS 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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/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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Determine the installed Windows version and build numberOpen Command Prompt or PowerShell and run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to get the exact build number (e.g., 10.0.19041.1165 for Windows 10 2004)Affected if The version matches one of the affected products and is below the fixed build number: Windows Server 2004 < 10.0.19041.1165, Server 2016 < 10.0.14393.4583, Server 2019 < 10.0.17763.2114, Server 20H2 < 10.0.19042.1165, or any Server 2008/2008 R2, 2012/2012 R2 version
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Verify whether the security update is installedRun 'wmic qfe list' or 'Get-HotFix | Select-Object HotFixID, InstalledOn' in PowerShell to list installed patches, then search for KB5004435 or any subsequent security update for this vulnerabilityAffected if The specific KB5004435 patch or a later cumulative update addressing this CVE is NOT installed
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Confirm the LSASS process is runningRun 'tasklist /FI "IMAGENAME eq lsass.exe"' or 'Get-Process lsass -ErrorAction SilentlyContinue' to verify the Local Security Authority Subsystem Service process is activeAffected if LSASS is running (which is default on affected Windows systems) and the version/patch check indicates the system is unpatched
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Assess network exposure of authentication servicesReview firewall rules or network configuration to determine if ports used by LSASS (such as LDAP, SMB authentication) are exposed to untrusted networks, using 'netsh advfirewall firewall show rule name=all' or equivalent network scanningAffected if The unpatched Windows system has LSASS-accessible ports (445, 389, 636, etc.) open to untrusted or external network segments
The system is likely affected if it runs an unpatched Windows Server or client version within the affected ranges and has network-accessible authentication services, even if LSASS itself is a local process because the vulnerability allows remote impersonation via specially crafted authentication requests.
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 · scoped10.0.14393.458310.0.17763.211410.0.19041.1165
Apply the Microsoft security update released in August 2021 for this vulnerability. Ensure Windows systems are fully patched and consider implementing additional controls such as enabling SMB signing and restricting NTLM authentication where possible.
Windows Server 2004: 10.0.19041.1165+ | Server 2016: 10.0.14393.4583+ | Server 2019: 10.0.17763.2114+ | Server 20H2: 10.0.19042.1165+
- Identify the current Windows Server version and build number using 'winver' or 'systeminfo'
- Apply the relevant Microsoft security update for CVE-2021-36942 from Windows Update or Microsoft Update Catalog
- For Windows Server 2008/2012: These versions are end-of-support; obtain Extended Security Updates (ESU) or migrate to a supported Windows Server version
- Reboot the server after applying the update
- Verify the installed build matches or exceeds the fixed version: 10.0.19041.1165 (Server 2004), 10.0.14393.4583 (Server 2016), 10.0.17763.2114 (Server 2019), or 10.0.19042.1165 (Server 20H2)
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-36942 — 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-2021-36942 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
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