# CVE-2026-1301: Out-of-bounds Write in o6 Automation GmbH Open62541

> A crafted JSON message in Open62541 with PubSub enabled causes an out-of-bounds write, leading to crashes or potential code execution.

- **Severity:** Medium 6.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/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:** A user has to click or open something
- **Fix available:** No
- **Published:** 5 Feb 2026
- **Updated:** 5 Feb 2026
- **Also known as:** GHSA-c8xh-89h3-73pj

## What is CVE-2026-1301?

CVE-2026-1301 is a medium-severity memory corruption vulnerability in o6 Automation GmbH Open62541, published on 5 Feb 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

In builds with PubSub and JSON enabled, a crafted JSON message can cause the decoder to write beyond a heap-allocated array before authentication, reliably crashing the process and corrupting memory.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-1301?


## How do I fix CVE-2026-1301?

No fix has been published for CVE-2026-1301 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-1301 being exploited?

There is no known exploitation of CVE-2026-1301 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-1301 and fix it if it is affected.

What it is: CVE-2026-1301 is a medium-severity memory corruption vulnerability in o6 Automation GmbH Open62541, published on 5 Feb 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-1301 in the wild and no public exploit code.

Affected product: o6 Automation GmbH Open62541. 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-2026-1301/ (Markdown: https://insights.sbomify.com/CVE-2026-1301/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-1301
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1301
- OSV: https://osv.dev/vulnerability/CVE-2026-1301

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-1301/
Summaries are generated and may contain mistakes; the official description above is the record.