# CVE-2026-51537: EIPStackGroup OpENer out-of-bounds read in Connection Manager

Source: https://junglewise.ai/threats/cve-2026-51537-eipstackgroup-opener-out-of-bounds-read-in-connection-manager  
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-2026-51537 · Severity: info · CVSS 7.5 · Published 2026-07-13

EIPStackGroup OpENer is an open-source implementation of the EtherNet/IP industrial protocol used to facilitate communication between industrial devices. A security vulnerability has been identified where a remote attacker can send a specially crafted network packet to crash the software. This results in a denial-of-service condition, potentially disrupting industrial operations and communication between connected equipment.

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

## Quick answers

**Is CVE-2026-51537 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-51537 being exploited in the wild.

**How severe is CVE-2026-51537?** 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-2026-51537?** 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-2026-51537 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-51537?** 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

An out-of-bounds read vulnerability exists in EIPStackGroup OpENer 2.3.0 (commit 76b95cf) within the Connection Manager's handling of ForwardOpen and LargeForwardOpen requests. The root cause is a 'parse-before-validate' logic error combined with missing boundary checks in low-level read helpers (e.g., GetByteFromMessage) located in cipconnectionmanager.c and cipconnectionobject.c. An unauthenticated remote attacker can establish a TCP connection to port 44818, register a session, and send a SendRRData packet with a malformed CIP request. If the request data is shorter than expected, the parser continues reading fields past the end of the stack-based receive buffer, leading to an AddressSanitizer-detected stack-buffer-overflow and process termination (Denial of Service).

## Affected products

- EIPStackGroup OpENer 2.3.0 (commit 76b95cf)

## Timeline

- 2026-04-23: disclosed: Issue reported on GitHub by MrAlaskan
- 2026-07-09: advisory: Detailed security advisory published by researcher
- 2026-07-13: advisory: CVE-2026-51537 published in NVD

## References

- [https://gist.github.com/MrAlaskan/a5fb0fb7765c9df80d28220ed558f04e](https://gist.github.com/MrAlaskan/a5fb0fb7765c9df80d28220ed558f04e)
- [https://github.com/EIPStackGroup/OpENer/issues/564](https://github.com/EIPStackGroup/OpENer/issues/564)

## 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)