# CVE-2020-12526: BECKHOFF: DoS-Vulnerability for TwinCAT OPC UA Server and IPC Diagnostics UA Server

> Attackers can cause denial of service in Beckhoff TwinCAT and IPC Diagnostics OPC UA servers by sending crafted requests, rendering the server unresponsive.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 13 May 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-53xf-f462-gx5v

## What is CVE-2020-12526?

CVE-2020-12526 is a medium-severity denial of service vulnerability in Beckhoff IPC Diagnostics UA Server, published on 13 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

TwinCAT OPC UA Server in versions up to 2.3.0.12 and IPC Diagnostics UA Server in versions up to 3.1.0.1 from Beckhoff Automation GmbH & Co. KG are vulnerable to denial of service attacks. The attacker needs to send several specifically crafted requests to the running OPC UA server. After some of these requests the OPC UA server is no longer responsive to any client. This is without effect to the real-time functionality of IPCs.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2020-12526?

It affects 3 products.


Products: Beckhoff Ipc Diagnostics Ua Server, Beckhoff Tf6100, Beckhoff Twincat Opc Ua Server.

## How do I fix CVE-2020-12526?

No fix has been published for CVE-2020-12526 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-12526 being exploited?

There is no known exploitation of CVE-2020-12526 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-12526 and fix it if it is affected.

What it is: CVE-2020-12526 is a medium-severity denial of service vulnerability in Beckhoff IPC Diagnostics UA Server, published on 13 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-12526 in the wild and no public exploit code.

Affected product: Beckhoff IPC Diagnostics 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-2020-12526/ (Markdown: https://insights.sbomify.com/CVE-2020-12526/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-12526
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-12526
- OSV: https://osv.dev/vulnerability/CVE-2020-12526

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-12526/
Summaries are generated and may contain mistakes; the official description above is the record.