# CVE-2026-19259: MZ Automation libiec61850 heap buffer overflow in MmsMapping

Source: https://junglewise.ai/threats/cve-2026-19259-mz-automation-libiec61850-heap-buffer-overflow-in-mmsmapping  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-08. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-19259 · Severity: medium · CVSS 5.3 · Published 2026-08-08

MZ Automation libiec61850 is a library used by industrial control system (ICS) client applications to communicate with power grid and utility servers using the IEC 61850 protocol. A malicious or compromised server can send a specially crafted response that triggers a heap buffer overflow in the client, causing the application to crash and denying service to operators who rely on these systems for monitoring and control.

Technologies: [MZ Automation libIEC61850](https://junglewise.ai/threats/technologies/libiec61850). Vendors: [MZ Automation](https://junglewise.ai/threats/vendors/mz-automation).

## Quick answers

**Is CVE-2026-19259 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-19259 being exploited in the wild.

**How severe is CVE-2026-19259?** Medium severity, with a CVSS score of 5.3, published 8 August 2026.

**Which products and versions are affected?** MZ Automation libIEC61850 up to 1.6.1.

**Is there a fix for CVE-2026-19259?** 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-2026-19259 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-19259?** Check whether you run MZ Automation libIEC61850 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

The vulnerability is a heap buffer over-read in the MmsMapping_varAccessSpecToObjectReference function (src/iec61850/common/iec61850_common.c, line 876) triggered by a malformed GetNamedVariableListAttributesResponse.itemId field. The vulnerable code assumes that decoded MMS names follow an internal LN$FC$... format and performs fixed-offset reads relative to the first '$' separator without validating the string length. When a malicious MMS server returns itemId="$" (two bytes: '$' and null terminator), the conversion routine reads past the allocated heap buffer. The attack is client-side, reachable during normal protocol operation (dataset directory enumeration), and requires network connectivity to a malicious or MITM-compromised MMS server. An attacker can cause denial of service by crashing libiec61850-based client applications. The project has not yet responded to the early disclosure.

## Affected products

- MZ Automation libiec61850 up to 1.6.1

## Timeline

- 2026-08-08: disclosed: CVE-2026-19259 published
- 2026-08-08: other: Exploit proof-of-concept available

## References

- [https://github.com/mz-automation/libiec61850/issues/599](https://github.com/mz-automation/libiec61850/issues/599)
- [https://github.com/user-attachments/files/29190426/PoC.zip](https://github.com/user-attachments/files/29190426/PoC.zip)

## Related threats

- [libIEC61850 invalid free in MMS report serialization](https://junglewise.ai/threats/cve-2026-68908-libiec61850-is-an-open-source-implementation-of-iec-61850-client)
- [libIEC61850 buffer over-read in dataset access handler](https://junglewise.ai/threats/cve-2026-68907-libiec61850-is-an-open-source-implementation-of-iec-61850-client)
- [libIEC61850 infinite loop in ACSE parseUserInformation](https://junglewise.ai/threats/cve-2026-68906-libiec61850-is-an-open-source-implementation-of-iec-61850-client)
- [libIEC61850 MMS ObtainFile double-free denial of service](https://junglewise.ai/threats/cve-2026-57446-libiec61850-is-an-open-source-implementation-of-iec-61850-client)
- [libIEC61850 NULL pointer dereference in MMS read service](https://junglewise.ai/threats/cve-2026-48741-libiec61850-is-an-open-source-implementation-of-iec-61850-client)