CVE-2021-21777
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 · uneditedAn information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Group OpENer 2.3 and development commit 8c73bf3. A specially crafted network request can lead to an out-of-bounds read.
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 confidenceAn information disclosure vulnerability exists in the Ethernet/IP UDP handler of OpENer 2.3 and development commit 8c73bf3. The vulnerability allows an attacker to send specially crafted network requests to trigger an out-of-bounds read, potentially exposing sensitive memory contents. The issue is in the UDP handler functionality specifically, indicating insufficient bounds checking when processing incoming UDP packets.
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
- Changed
- Confidentiality
- High
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/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 deploymentIdentify whether OpENer (Ethernet/IP industrial communication server) is present on the system. Check running processes, services, or installed packages for OpENer or related Ethernet/IP server components.Affected if OpENer software is installed and running
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Verify OpENer version is 2.3Determine the installed version of OpENer. Check version strings in binaries, configuration files, documentation, or application metadata to confirm the exact version.Affected if Version equals 2.3 exactly (development commit 8c73bf3 is also affected)
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Confirm UDP handler is enabledCheck if the Ethernet/IP UDP handler functionality is active. Review network configurations, service settings, or logs to determine if UDP-based Ethernet/IP communication is enabled and listening for incoming UDP packets.Affected if UDP handler for Ethernet/IP is enabled and processing incoming UDP packets
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Assess network exposure of UDP serviceDetermine if the system is accepting UDP packets on the Ethernet/IP ports from network sources. Use netstat, ss, or similar tools to check for listening UDP sockets and evaluate whether they are bound to interfaces accessible from untrusted networks.Affected if UDP service is exposed to untrusted or external network segments
Environment is affected only if OpENer version 2.3 is running with the Ethernet/IP UDP handler enabled and accessible from the network.
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 vendor patches or update to a patched version of OpENer. If no patch available, implement input validation and bounds checking in the UDP packet handler to ensure all memory reads stay within allocated buffers. Consider network segmentation to limit exposure of affected systems.
- 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-2021-21777 — 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-2021-21777 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
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