# CVE-2021-34594: Beckhoff: Relative path traversal vulnerability through TwinCAT OPC UA Server

> Administrators can exploit relative path traversal to create or delete arbitrary files on the system via the TwinCAT OPC UA Server.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Nov 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-pjgx-r654-8vfq

## What is CVE-2021-34594?

CVE-2021-34594 is a medium-severity path traversal vulnerability in Beckhoff Automation TwinCAT OPC UA Server, published on 4 Nov 2021. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

TwinCAT OPC UA Server in TF6100 and TS6100 in product versions before 4.3.48.0 or with TcOpcUaServer versions below 3.2.0.194 are prone to a relative path traversal that allow administrators to create or delete any files on the system.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), CWE-23 (Relative Path Traversal)

## Which versions are affected by CVE-2021-34594?

It affects 2 products.


Products: Beckhoff Tf6100 Firmware, Beckhoff Ts6100 Firmware.

## How do I fix CVE-2021-34594?

No fix has been published for CVE-2021-34594 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34594 being exploited?

There is no known exploitation of CVE-2021-34594 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34594 and fix it if it is affected.

What it is: CVE-2021-34594 is a medium-severity path traversal vulnerability in Beckhoff Automation TwinCAT OPC UA Server, published on 4 Nov 2021. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-34594 in the wild and no public exploit code.

Affected product: Beckhoff Automation TwinCAT OPC UA Server. 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-2021-34594/ (Markdown: https://insights.sbomify.com/CVE-2021-34594/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34594
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34594
- OSV: https://osv.dev/vulnerability/CVE-2021-34594

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-34594/
Summaries are generated and may contain mistakes; the official description above is the record.