CVE-2026-51536: Integer Overflow (CVSS 9.1)

Description

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.

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CVSS v3.1 Score

9.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

EPSS — Exploit Prediction

0.0019

Probability of exploitation

0.09%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-190 Integer Overflow

References

Other References

https://gist.github.com/MrAlaskan/e160c626a32e03e5d9eddaa732560672 https://github.com/EIPStackGroup/OpENer/issues/563 https://github.com/EIPStackGroup/OpENer/issues/563

Frequently Asked Questions

What is CVE-2026-51536? +

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. It has a CVSS v3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-51536? +

CVE-2026-51536 has a CVSS v3.1 score of 9.1 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0019, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-51536? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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