# CVE-2026-51221: EIPStackGroup OpENer buffer overflow in Get_Attribute_List

Source: https://junglewise.ai/threats/cve-2026-51221-eipstackgroup-opener-buffer-overflow-in-get-attribute-list  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-29. Updated: 2026-06-29  
License: CC BY 4.0 with a link back

CVE-2026-51221 · Severity: info · CVSS 7.5 · Published 2026-06-29

OpENer is an open-source software stack used by industrial devices to communicate over the EtherNet/IP protocol. A security flaw allows a remote attacker to crash the software by sending a specially crafted network packet. This could lead to a denial-of-service (DoS) condition, disrupting industrial operations or communication between automated devices.

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

## Quick answers

**Is CVE-2026-51221 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-51221 being exploited in the wild.

**How severe is CVE-2026-51221?** Informational severity, with a CVSS score of 7.5, published 29 June 2026.

**Which products and versions are affected?** EIPStackGroup OpENer commit 76b95cf951a18d0e8481833168ab8c6943ce7c96.

**Is there a fix for CVE-2026-51221?** 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-2026-51221 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-51221?** 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 buffer overflow exists in the Get_Attribute_List function within EIPStackGroup OpENer (specifically commit 76b95cf). The vulnerability is triggered when the stack processes a malformed Common Packet Format (CPF) packet with an inconsistent item count. During response re-assembly in EncodeMessageRouterResponseData, the software fails to validate destination capacity before copying an oversized Message Router response into the ENIPMessage buffer. This results in an out-of-bounds write that corrupts the adjacent current_message_position pointer, leading to a segmentation fault and denial of service when the corrupted pointer is later dereferenced in AddIntToMessage. The attack is reachable over the network without authentication.

## Affected products

- EIPStackGroup OpENer commit 76b95cf951a18d0e8481833168ab8c6943ce7c96

## Timeline

- 2026-06-29: disclosed: Vulnerability reported via GitHub issues and published to NVD.

## References

- [https://github.com/EIPStackGroup/OpENer](https://github.com/EIPStackGroup/OpENer)
- [https://github.com/EIPStackGroup/OpENer/issues/567](https://github.com/EIPStackGroup/OpENer/issues/567)

## 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)