# CVE-2019-16871: Auth bypass in n/a

> Attackers can achieve remote code execution with SYSTEM privileges on Beckhoff PLCs and engineering stations via the ADS protocol.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Dec 2019
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-2q68-c93j-vxw8

## What is CVE-2019-16871?

CVE-2019-16871 is a critical authentication bypass vulnerability in n/a, published on 19 Dec 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Beckhoff Embedded Windows PLCs through 3.1.4024.0, and Beckhoff Twincat on Windows Engineering stations, allow an attacker to achieve Remote Code Execution (as SYSTEM) via the Beckhoff ADS protocol.

Weakness: CWE-290 (Authentication Bypass by Spoofing)

## Which versions are affected by CVE-2019-16871?

It affects 1 product.


Products: Beckhoff Twincat.

## How do I fix CVE-2019-16871?

No fix has been published for CVE-2019-16871 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-16871 being exploited?

There is no known exploitation of CVE-2019-16871 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2017-16726](https://insights.sbomify.com/CVE-2017-16726/): Weak cryptography in Beckhoff TwinCAT (critical 9.1)
- [CVE-2018-7502](https://insights.sbomify.com/CVE-2018-7502/): Privilege escalation in Beckhoff TwinCAT PLC products (high 7.8)
- [CVE-2019-5637](https://insights.sbomify.com/CVE-2019-5637/): Beckhoff TwinCAT Profinet Driver Divide-by-Zero Denial of Service (high 7.5)
- [CVE-2017-16718](https://insights.sbomify.com/CVE-2017-16718/): Weak cryptography in Beckhoff TwinCAT (medium 5.9)
- [CVE-2020-12494](https://insights.sbomify.com/CVE-2020-12494/): Beckhoff: Etherleak in TwinCAT RT network driver (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-16871 and fix it if it is affected.

What it is: CVE-2019-16871 is a critical authentication bypass vulnerability in n/a, published on 19 Dec 2019. 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-2019-16871 in the wild and no public exploit code.

Affected product: n/a. 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-2019-16871/ (Markdown: https://insights.sbomify.com/CVE-2019-16871/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-16871
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-16871
- OSV: https://osv.dev/vulnerability/CVE-2019-16871

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-16871/
Summaries are generated and may contain mistakes; the official description above is the record.