# CVE-2026-66349: MZ Automation libiec61850 Out-of-bounds Read

> An attacker can cause a denial of service in the MMS server by sending a malformed BER-encoded request that triggers an out-of-bounds read.

- **Severity:** Medium 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`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 30 Jul 2026
- **Updated:** 31 Jul 2026
- **Also known as:** GHSA-8m3p-4g59-6h2r

## What is CVE-2026-66349?

CVE-2026-66349 is a medium-severity memory corruption vulnerability in MZ Automation GmbH libiec61850, published on 30 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-66349?


## How do I fix CVE-2026-66349?

No fix has been published for CVE-2026-66349 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-66349 being exploited?

There is no known exploitation of CVE-2026-66349 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66349 and fix it if it is affected.

What it is: CVE-2026-66349 is a medium-severity memory corruption vulnerability in MZ Automation GmbH libiec61850, published on 30 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-66349 in the wild and no public exploit code.

Affected product: MZ Automation GmbH libiec61850. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-66349/ (Markdown: https://insights.sbomify.com/CVE-2026-66349/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66349
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66349
- OSV: https://osv.dev/vulnerability/CVE-2026-66349

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66349/
Summaries are generated and may contain mistakes; the official description above is the record.