CVE-2026-51221
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 buffer overflow in the Get_Attribute_List function of EIPStackGroup OpENer commit 76b95c allows attackers to cause a Denial of Service (DoS) via supplying a crafted Common Packet Format (CPF) packet.
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 buffer overflow vulnerability exists in the Get_Attribute_List function of the OpENer EtherNet/IP stack implementation. The flaw is triggered when processing specially crafted Common Packet Format (CPF) packets, allowing remote attackers to cause a Denial of Service by overflowing a buffer in the affected function.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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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Confirm OpENer EtherNet/IP stack deploymentIdentify if OpENer is installed in your environment by searching for files named 'OpENer', 'OPENER', or 'EtherNetIP' in your system, or by checking running processes for OpENer-related servicesAffected if OpENer EtherNet/IP stack is present and running
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Determine OpENer versionLocate version information in the OpENer installation directory, typically found in version.h, README files, or the binary metadata. Compare your version against any known patched versionsAffected if Version is older than the patched release containing the fix for CVE-2026-51221
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Verify CPF packet processing is enabledInspect the OpENer configuration files or running parameters to confirm that Common Packet Format (CPF) packet processing is enabled, as this is the attack vectorAffected if CPF packet processing is enabled and exposed to network traffic
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Check if Get_Attribute_List is accessibleReview network exposure and access controls for the Get_Attribute_List function. This function handles attribute queries and processes incoming CIP/EtherNet/IP requestsAffected if Get_Attribute_List function can receive external network requests without proper input validation
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Inspect network listening servicesExamine open ports and services listening for EtherNet/IP communications (typically ports 44818 or 2222). Identify if OpENer is bound to these interfacesAffected if OpENer EtherNet/IP services are listening on accessible network interfaces
Your environment is affected if OpENer EtherNet/IP stack is deployed, the version lacks the CVE-2026-51221 patch, and CPF packet processing is exposed to network traffic that can reach the Get_Attribute_List function.
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 vendor patch for OpENer that addresses the buffer overflow vulnerability in Get_Attribute_List, or implement input validation on CPF packets to ensure proper bounds checking before processing.
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 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 $4,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-51221 — 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-2026-51221 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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