# CVE-2026-66720: MZ Automation GmbH libiec61850 heap out-of-bounds read in GOOSE subscriber

Source: https://junglewise.ai/threats/cve-2026-66720-mz-automation-gmbh-libiec61850-heap-out-of-bounds-read-in-goose  
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-2026-66720 · Severity: medium · CVSS 6.5 · Published 2026-07-30

A vulnerability exists in a specialized communication library used in energy and industrial control systems. An attacker on the same local network could send a malicious message that causes the system to crash. This would result in a denial-of-service, potentially disrupting critical infrastructure operations and monitoring.

## Quick answers

**Is CVE-2026-66720 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-66720 being exploited in the wild.

**How severe is CVE-2026-66720?** 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-2026-66720?** A patch was published on 2026-07-30: Fixed in version 1.6.2 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-66720 attacked?** It is attacked from the adjacent network, in a software library.

**Am I affected by CVE-2026-66720?** 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

The vulnerability is a heap out-of-bounds read (CWE-125) located within the GOOSE subscriber component of libiec61850. The root cause is improper validation of the UTC timestamp field in unauthenticated IEC 61850 GOOSE (EtherType 0x88B8) Layer-2 multicast messages. An attacker can trigger this by sending a specially crafted GOOSE frame containing an undersized timestamp field. Successful exploitation allows an unauthenticated attacker on the adjacent network to crash the subscriber process, resulting in a denial-of-service (DoS) condition. 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: patched: Fixed in version 1.6.2

## 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)