# CVE-2026-66364: MZ Automation GmbH libiec61850 out-of-bounds read in GOOSE parser

Source: https://junglewise.ai/threats/cve-2026-66364-mz-automation-gmbh-libiec61850-out-of-bounds-read-in-goose-parser  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-30. Updated: 2026-07-30  
License: CC BY 4.0 with a link back

CVE-2026-66364 · Severity: medium · CVSS 6.5 · Published 2026-07-30

A vulnerability exists in a specialized communication library used in energy infrastructure and industrial control systems. An attacker on the local network can send a single malicious message that crashes the system's communication service. This results in a denial-of-service, potentially disrupting the monitoring and control of power grid equipment.

## Quick answers

**Is CVE-2026-66364 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-66364 being exploited in the wild.

**How severe is CVE-2026-66364?** Medium severity, with a CVSS score of 6.5, published 30 July 2026.

**Which products and versions are affected?** MZ Automation GmbH libiec61850 < 1.6.2.

**Is there a fix for CVE-2026-66364?** 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-2026-66364 attacked?** It is attacked from the adjacent network, in a software library.

**Am I affected by CVE-2026-66364?** Check whether anything you run is named in the advisory. 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 boundary handling flaw exists in the GOOSE payload parser of libiec61850 before version 1.6.2. The vulnerability is triggered when an attacker-controlled inner element length exceeds its enclosing length within a Layer 2 multicast frame (EtherType 0x88B8). This leads to a one-byte heap out-of-bounds read (CWE-125). Exploitation reliably terminates the subscriber process, resulting in a denial-of-service condition. The attack requires no authentication but must be launched from the same local network segment (process bus). The issue is resolved in version 1.6.2.

## Affected products

- MZ Automation GmbH libiec61850 < 1.6.2

## Timeline

- 2026-07-30: advisory
- 2026-07-30: disclosed

## References

- [https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-211-10.json](https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-211-10.json)
- [https://www.cisa.gov/news-events/ics-advisories/icsa-26-211-10](https://www.cisa.gov/news-events/ics-advisories/icsa-26-211-10)