# CVE-2026-51536: EIPStackGroup OpENer stack buffer overflow in CIP message router

Source: https://junglewise.ai/threats/cve-2026-51536-eipstackgroup-opener-stack-buffer-overflow-in-cip-message-router  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-13. Updated: 2026-07-13  
License: CC BY 4.0 with a link back

CVE-2026-51536 · Severity: info · CVSS 7.5 · Published 2026-07-13

OpENer is an open-source implementation of the EtherNet/IP protocol used in industrial automation and control systems. A vulnerability in how the software handles network messages could allow a remote attacker to crash the service by sending a specially crafted packet. This results in a denial-of-service condition, potentially disrupting industrial operations and communication between devices on the factory floor.

Technologies: [EIPStackGroup OpENer](https://junglewise.ai/threats/technologies/opener). Vendors: [EIPStackGroup](https://junglewise.ai/threats/vendors/eipstackgroup).

## Quick answers

**Is CVE-2026-51536 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-51536 being exploited in the wild.

**How severe is CVE-2026-51536?** Informational severity, with a CVSS score of 7.5, published 13 July 2026.

**Which products and versions are affected?** EIPStackGroup OpENer 2.3.0 (commit 76b95cf).

**Is there a fix for CVE-2026-51536?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-51536 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-51536?** Check whether you run EIPStackGroup OpENer at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A stack-based buffer overflow exists in OpENer 2.3.0 (commit 76b95cf) within the CIP message router and EPATH decoding logic. The vulnerability is caused by inconsistent integer typing where a 32-bit 'int' length is passed to functions expecting a 16-bit signed 'EipInt16', leading to truncation and negative values. These negative values bypass unsigned bounds checks (CWE-194) and result in an underflow when calculating remaining data size. A remote, unauthenticated attacker can trigger this by sending a crafted SendUnitData request over TCP port 44818, leading to a crash in DecodePaddedEPath.

## Affected products

- EIPStackGroup OpENer 2.3.0 (commit 76b95cf)

## Timeline

- 2026-04-23: disclosed: Issue reported on GitHub by MrAlaskan
- 2026-07-13: advisory: NVD published CVE-2026-51536

## References

- [https://gist.github.com/MrAlaskan/e160c626a32e03e5d9eddaa732560672](https://gist.github.com/MrAlaskan/e160c626a32e03e5d9eddaa732560672)
- [https://github.com/EIPStackGroup/OpENer/issues/563](https://github.com/EIPStackGroup/OpENer/issues/563)

## Related threats

- [OpENer out-of-bounds read in EtherNet/IP ForwardOpen parser](https://junglewise.ai/threats/cve-2026-75353-opener-v2-3-commit-76b95cf-contains-an-out-of-bounds-read-in-the)
- [OpENer out-of-bounds read in ForwardOpen connection-path parser](https://junglewise.ai/threats/cve-2026-75351-opener-v2-3-commit-76b95cf-contains-an-out-of-bounds-read-in-the)
- [EIPStackGroup OpENer buffer overflow in GetAttributeList](https://junglewise.ai/threats/cve-2026-75350-eipstackgroup-opener-v2-3-master-commit-76b95cf-contains-a-buffer)
- [EIPStackGroup OpENer expired pointer dereference in EtherNet/IP CPF](https://junglewise.ai/threats/cve-2026-75347-eipstackgroup-opener-v2-3-and-master-up-to-commit-76b95cf-contain)
- [EIPStackGroup OpENer out-of-bounds read in Connection Manager](https://junglewise.ai/threats/cve-2026-75349-eipstackgroup-opener-v2-3-0-master-up-to-commit-76b95cf-contains)