CVE-2021-1671
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 · uneditedRemote Procedure Call Runtime Remote Code Execution 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 Remote Procedure Call (RPC) Runtime vulnerability that allows remote attackers to execute arbitrary code on affected systems. The vulnerability exists in the RPC runtime component, which is a fundamental Windows networking service used for inter-process communication.
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
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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 the Windows versionRun 'winver' from the Run dialog, or execute 'systeminfo' in Command Prompt and look at the OS Name and Version fieldsAffected if The operating system is Windows 7, Windows 8.1, Windows 10 (any version), Windows Rt 8.1, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2, Windows Server 2016, Windows Server 2019, or Windows Server 20H2 - these are all in the affected product list
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Confirm the RPC Runtime service is present and runningOpen Services (services.msc), locate 'Remote Procedure Call (RPC)' and 'Remote Procedure Call (RPC) Locator' services, and verify their Status is Running. Alternatively, run 'sc query rpcss' and 'sc query RpcLocator' from an elevated command promptAffected if Both RPC services are Running - the vulnerability exists in the RPC runtime component which requires these services to be active
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Check for the security update installed for this CVEOpen Control Panel > Programs and Features > View installed updates, or run 'wmic qfe list' from Command Prompt. Look for update KB5000802 (March 2021) or subsequent related RPC security updates. The exact KB varies by Windows versionAffected if The specific security update for CVE-2021-1671 is NOT installed - the system remains vulnerable
If the system runs any affected Windows version listed and the CVE-2021-1671 security update is missing, the environment is vulnerable to remote code execution via the RPC runtime.
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-2021-1671. If patches are unavailable, consider restricting RPC communications to trusted networks and implementing network segmentation to limit exposure.
- 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-2021-1671 — 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-2021-1671 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