# CVE-2026-63550: MZ Automation libiec61850 Out-of-bounds Read

> A crafted BER-encoded message can cause a heap out-of-bounds read in the MMS decoder, leading to a denial-of-service in IEC 61850 systems.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 30 Jul 2026
- **Updated:** 31 Jul 2026
- **Also known as:** GHSA-mgh9-x48v-5vx9

## What is CVE-2026-63550?

CVE-2026-63550 is a high-severity memory corruption vulnerability in MZ Automation GmbH libiec61850, published on 30 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The MMS BER decoder contains a boundary-handling flaw in the processing 
of certain fields within confirmed-request messages. When a crafted 
BER-encoded element is received over an established MMS session (TCP 
port 102), the decoder may advance its internal read position 
incorrectly, leading to a heap out-of-bounds read. This condition causes
 the MMS handling process to terminate unexpectedly, resulting in a 
denial-of-service.

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

## Which versions are affected by CVE-2026-63550?


## How do I fix CVE-2026-63550?

No fix has been published for CVE-2026-63550 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-63550 being exploited?

There is no known exploitation of CVE-2026-63550 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63550 and fix it if it is affected.

What it is: CVE-2026-63550 is a high-severity memory corruption vulnerability in MZ Automation GmbH libiec61850, published on 30 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-63550 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-2026-63550/ (Markdown: https://insights.sbomify.com/CVE-2026-63550/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63550
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63550
- OSV: https://osv.dev/vulnerability/CVE-2026-63550

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63550/
Summaries are generated and may contain mistakes; the official description above is the record.