# CVE-2020-12510: Beckhoff: Privilege Escalation through TwinCat System

> A local attacker can replace a system executable to execute arbitrary code with higher privileges when another user logs in.

- **Severity:** High 7.3 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 19 Nov 2020
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-63jm-rmjc-h9qh

## What is CVE-2020-12510?

CVE-2020-12510 is a high-severity vulnerability in Beckhoff TwinCat XAR 3.1, published on 19 Nov 2020. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

The default installation path of the TwinCAT XAR 3.1 software in all versions is underneath C:\TwinCAT. If the directory does not exist it and further subdirectories are created with permissions which allow every local user to modify the content. The default installation registers TcSysUI.exe for automatic execution upon log in of a user. If a less privileged user has a local account he or she can replace TcSysUI.exe. It will be executed automatically by another user during login. This is also true for users with administrative access. Consequently, a less privileged user can trick a higher privileged user into executing code he or she modified this way. By default Beckhoff’s IPCs are shipped with TwinCAT software installed this way and with just a single local user configured. Thus the vulnerability exists if further less privileged users have been added.

Weakness: CWE-276 (Incorrect Default Permissions)

## Which versions are affected by CVE-2020-12510?

It affects 1 product.


Products: Beckhoff Twincat Extended Automation Runtime.

## How do I fix CVE-2020-12510?

No fix has been published for CVE-2020-12510 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-12510 being exploited?

There is no known exploitation of CVE-2020-12510 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-12510 and fix it if it is affected.

What it is: CVE-2020-12510 is a high-severity vulnerability in Beckhoff TwinCat XAR 3.1, published on 19 Nov 2020. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2020-12510 in the wild and no public exploit code.

Affected product: Beckhoff TwinCat XAR 3.1. 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-2020-12510/ (Markdown: https://insights.sbomify.com/CVE-2020-12510/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-12510
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-12510
- OSV: https://osv.dev/vulnerability/CVE-2020-12510

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-12510/
Summaries are generated and may contain mistakes; the official description above is the record.