CVE-2021-27500
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 · uneditedA specifically crafted packet sent by an attacker to EIPStackGroup OpENer EtherNet/IP commits and versions prior to Feb 10, 2021 may result in a denial-of-service condition.
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 confidenceA specifically crafted packet sent to EIPStackGroup OpENer EtherNet/IP implementations (versions prior to Feb 10, 2021) can trigger a denial-of-service condition, causing the service to become unavailable.
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<= 2.3CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 if OpENer is installedSearch for OpENer-related processes, services, or installed packages on the system. Look for process names containing 'Opener', 'EIPStackGroup', or 'EtherNet/IP' in running processes or installed software listings.Affected if OpENer or EIPStackGroup OpENer software is found running or installed on the system
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Determine the installed OpENer versionLocate the OpENer binary or installation directory and check its version information. Common methods include using 'rpm -qi' or 'dpkg -l' for package-based installations, or checking version strings in the binary itself if directly executed.Affected if The version is 2.3 or earlier, or the version cannot be determined (treated as vulnerable)
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Check if EtherNet/IP service is activeVerify whether the OpENer EtherNet/IP service is currently running and listening on network ports. Inspect active network listeners using commands like 'netstat' or 'ss' looking for EtherNet/IP typical ports (typically UDP/TCP ports in the industrial protocol range).Affected if The EtherNet/IP service is running and accepting network connections
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Verify installation dateCheck the installation timestamp of the OpENer software package or binary file creation date using filesystem metadata. Compare against February 10, 2021.Affected if The software was installed or last updated prior to February 10, 2021
The environment is affected if OpENer version 2.3 or earlier is installed, or if the installation predates February 10, 2021, and the EtherNet/IP service is active and network-accessible.
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 dataUpgrade to the patched version of OpENer released after February 10, 2021.
- Consultation4.0 h
- Implementation2.0 h
- Testing8.0 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 $4,352.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-27500 — 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-2021-27500 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