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OpenerApplication · Opener Project

CVE-2026-51536

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
In OpENer 2.3.0 (commit 76b95cf) when parsing incoming CIP (Common Industrial Protocol) network packets, the length parameter is inconsistently typed across the call stack. Specifically, an upstream length calculated as an int is passed to a downstream function that expects an EipInt16 (a 16-bit signed integer). If a maliciously crafted packet with specific length fields is processed, the length parameter can overflow or be truncated into a negative value. This negative length bypasses subsequent bounds checking (due to signed/unsigned comparison issues) and is ultimately used in memory operations, leading to a Stack Buffer Overflow when reading data in DecodePaddedEPath.

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 a stack buffer overflow in DecodePaddedEPath caused by an integer type mismatch during CIP packet parsing. An upstream length value calculated as a standard int is passed to a downstream function expecting EipInt16 (16-bit signed), causing overflow/truncation to a negative value that bypasses bounds checks due to signed/unsigned comparison issues.

MitigationUpgrade to a patched version of OpENer that properly handles length parameter typing across the call stack, or implement input validation to reject packets with length fields that would cause truncation/overflow.

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 version
    Check the version string in the OpENer binary, header files, or application startup logs. Common locations: version.h, README, or console output on launch.
    Affected if Version is 2.3.0 or if the version cannot be determined and the software performs CIP packet parsing.
  2. Confirm CIP/EtherNet/IP parsing is enabled
    Review the OpENer build configuration or runtime settings for flags related to CIP message routing, Explicit Messaging, or ENIP communication. Check if the CIP stack is compiled into the binary.
    Affected if CIP packet parsing functionality is present and active in the deployment.
  3. Locate DecodePadedEPath function
    Search the OpENer binary or source code for the DecodePaddedEPath function. In source, check CIP_Handle.c or similar CIP handling source files. In binary, use strings or a disassembler to locate this function symbol.
    Affected if The DecodePaddedEPath function exists in the compiled binary and handles EPath decoding during CIP communication.
  4. Verify signed/unsigned length handling
    Inspect the code where DecodePaddedEPath is called, specifically the length parameter passed to it. Look for assignments where a standard int length value is cast or passed to an EipInt16 (16-bit signed) parameter.
    Affected if The code passes an int-typed length value to a function expecting EipInt16 without proper bounds validation, enabling truncation to negative values.
  5. Check bounds check logic in packet processing
    Examine the bounds checking logic within or near DecodePaddedEPath. Determine if comparisons involve mixed signed/unsigned types (e.g., signed length vs. unsigned buffer size) that could be bypassed by negative truncated values.
    Affected if Bounds checks use unsigned comparisons against a length parameter that could become negative due to truncation.

You are affected if OpENer version 2.3.0 is in use with CIP packet parsing enabled, and the DecodePaddedEPath function processes incoming CIP packets without proper validation that the length parameter cannot truncate to a negative value.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to a patched version of OpENer that properly handles length parameter typing across the call stack, or implement input validation to reject packets with length fields that would cause truncation/overflow.

Fix this in Opener Scoped from the published advisory
  • Consultation6.0 h
  • Implementation10.0 h
  • Testing12.0 h
  • Review / QA6.0 h
34.0 hours of engineering $5,880
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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-2026-51536 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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