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OpenerApplication · Opener Project

CVE-2026-51537

CRITICAL · 9.1 CVSS v3.1 Published 2026-07-13
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 5 weeks old

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 · unedited
EIPStackGroup OpENer 2.3.0 (commit 76b95cf) has an out-of-bounds read issue in Connection Manager handling of ForwardOpen requests when processing short malformed packets. An attacker can send a valid ENIP outer frame carrying a malformed CIP ForwardOpen/LargeForwardOpen request, causing the parser to continue reading fields even when request data is insufficient. This issue is remotely triggerable via network traffic and does not require authentication.

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 · high confidence

OpENer 2.3.0 contains an out-of-bounds read vulnerability in the Connection Manager's ForwardOpen/LargeForwardOpen request handling. When processing malformed CIP requests embedded in ENIP frames with insufficient data, the parser continues reading fields beyond the packet boundaries, causing memory corruption.

MitigationImplement rigorous input validation: validate total packet length against expected request size before parsing any fields, reject packets with insufficient data, and add explicit bounds checks before each field read operation in the CIP request parser.

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
OpenerApplication
Affected:= 2.3.0

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
High
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify OpENer installation and version
    Locate the OpENer application or library files on the system and determine the installed version (typically found in application metadata, binary properties, or version information files). Compare the found version against the affected version 2.3.0.
    Affected if OpENer version 2.3.0 is installed and running.
  2. Verify Connection Manager is active
    Check if the OpENer Connection Manager component is enabled and processing CIP requests. This can be confirmed by reviewing the application configuration or runtime status to confirm CIP ForwardOpen and LargeForwardOpen request handling is active.
    Affected if Connection Manager is enabled and configured to process CIP ForwardOpen/LargeForwardOpen requests.
  3. Confirm CIP communication ports are open
    Inspect network listener configuration to determine if CIP ports (default 44818 for EtherNet/IP) are open and accepting connections. Use network scanning or port inspection tools to identify listening services.
    Affected if CIP ports are open and accessible, allowing external network packets to reach the OpENer service.
  4. Check for unauthenticated network access
    Evaluate network accessibility of the CIP service. Determine if the service is exposed to untrusted networks or if proper network segmentation restricts access to authorized endpoints only.
    Affected if The CIP service is reachable from untrusted network segments without authentication requirements.

You are affected if OpENer version 2.3.0 is running with Connection Manager processing CIP ForwardOpen/LargeForwardOpen requests and the CIP port is network-accessible to potential attackers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement rigorous input validation: validate total packet length against expected request size before parsing any fields, reject packets with insufficient data, and add explicit bounds checks before each field read operation in the CIP request parser.

Recommended fix Moderate confidence

Latest stable release of EIPStackGroup OpENer (verify releases >2.3.0 on github.com/EIPStackGroup/OpENer)

  1. 1. Identify the current OpENer version in use by checking the source code or build artifacts
  2. 2. Navigate to the official EIPStackGroup OpENer GitHub repository at github.com/EIPStackGroup/OpENer
  3. 3. Review the release page to identify the latest stable release version that includes fixes after commit 76b95cf
  4. 4. Download or clone the latest stable release version
  5. 5. Replace the vulnerable OpENer binaries or source code with the new version
  6. 6. Rebuild and redeploy the application following the project's build instructions
  7. 7. Verify the deployment and test that legitimate CIP ForwardOpen operations still function correctly
Caveat Review release notes for any API or configuration changes between 2.3.0 and the target version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Opener Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-51537 in production — separate from our analysis above.

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What this is

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.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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