CVE-2026-51538
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 · uneditedEIPStackGroup OpENer 2.3.0 (commit 76b95cf) suffers from an Incorrect Access Control vulnerability in its handling of encapsulation sessions. When the server processes critical encapsulation commands, it verifies whether the provided session_handle exists in the global session list, but it fails to verify whether that handle belongs to the specific TCP connection issuing the request. Because there is no strong binding between a session handle and its originating socket, any attacker on the network can use a valid session handle created by another legitimate client to bypass access controls.
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 confidenceEIPStackGroup OpENer 2.3.0 has an incorrect access control vulnerability where session handles are validated against a global session list without verifying the handle belongs to the specific TCP connection making the request. This allows any network attacker to hijack a valid session handle from another legitimate client and bypass access controls.
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= 2.3.0CVSS 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
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
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 installation and versionIdentify if EIPStackGroup OpENer software is installed and determine the installed version. Common methods include checking application binaries, libraries, or running processes (e.g., ps aux | grep OpENer, or inspecting installed package information).Affected if The installed version is 2.3.0 specifically.
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Verify session handling is enabledDetermine whether the OpENer service has session management functionality active. This may involve reviewing runtime configuration, examining if session-related code/modules are loaded, or checking if the service is configured to handle CIP sessions (look for session creation, session handle allocation, or CIP connection manager activity in logs or config).Affected if Session handling is enabled and the service processes CIP session requests.
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Assess network exposure of the OpENer serviceCheck if the OpENer service is listening on network ports (typically Ethernet/IP ports 44818 or 2222) and accessible from network interfaces. Use commands like netstat, ss, or nmap to identify listening ports and bound addresses. Determine if the service accepts connections from untrusted or external network segments.Affected if The service is exposed to network attackers (e.g., accessible on non-localhost interfaces or across network segments with untrusted clients).
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Inspect active session stateIf the service is running, observe if active CIP sessions exist. Check for session handle allocation in memory, logs, or runtime diagnostics. The vulnerability allows an attacker to use a valid session handle from any connection, so active legitimate sessions are the target for hijacking.Affected if There are active sessions from legitimate clients that could be targeted for handle hijacking.
If OpENer version 2.3.0 is running with session handling enabled and exposed to network attackers, the environment is affected by this session hijacking vulnerability.
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 dataImplement strong session-to-connection binding by associating each session handle with its originating socket/connection and validating both the handle and the connection identity on each request.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-51538 — 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-2026-51538 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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- Version or environment caveats, and links to real fixes
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