# CVE-2026-66349 — MZ Automation GmbH libiec61850

> As of 2026-07-31, CVE-2026-66349 is a MEDIUM-severity vulnerability in MZ Automation GmbH libiec61850, CVSS v3.1 6.5, EPSS 0.1% (7.9th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-66349 as of 2026-07-31; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-07-31

## What is CVE-2026-66349?

The MMS server connection handler contains a flaw in its processing of BER-encoded request data. When an MMS confirmed request PDU containing an extended BER tag is received over an established session, the decoder may advance its internal buffer incorrectly due to a missing bounds check. This results in a one byte heap out-of-bounds read and causes the MMS service process to terminate, leading to a denial-of-service condition.

The record classifies CVE-2026-66349 under weakness class [CWE-125](https://intel.threadlinqs.com/cwe/CWE-125). Its CVSS v3 base vector states that the flaw is reachable from an adjacent network, needs no prior authentication, needs no user interaction, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 67 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 6.5 — MEDIUM (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **CVSS v4.0 base score:** 6.9 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 7.9% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3.6/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-30, last modified 2026-07-31

## Is CVE-2026-66349 being exploited?

It currently carries a trending score of 31 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [MZ Automation GmbH](https://intel.threadlinqs.com/vendors/mz-automation): libiec61850

## How to fix CVE-2026-66349

No vendor patch reference has been recorded for CVE-2026-66349 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-66349

No threat campaign in the Threadlinqs corpus currently references CVE-2026-66349, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-08-03. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

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

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-66349
Full detection coverage and IOCs for threats exploiting CVE-2026-66349 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp