# CVE-2023-33921: Auth bypass in CP-8031 MASTER MODULE

> An attacker with physical access can brute-force the root password via an exposed UART console to gain full control of Siemens master modules.

- **Severity:** Medium 6.8 (`CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 13 Jun 2023
- **Updated:** 13 Feb 2025
- **Also known as:** GHSA-hpw2-7w94-ff35

## What is CVE-2023-33921?

CVE-2023-33921 is a medium-severity authentication bypass vulnerability in Siemens CP-8031 MASTER MODULE, published on 13 Jun 2023. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability has been identified in CP-8031 MASTER MODULE (All versions < CPCI85 V05), CP-8050 MASTER MODULE (All versions < CPCI85 V05). The affected devices contain an exposed UART console login interface. An attacker with direct physical access could try to bruteforce or crack the root password to login to the device.

Weakness: CWE-749 (Exposed Dangerous Method or Function)

## Which versions are affected by CVE-2023-33921?

It affects 1 product.


Products: Siemens Cpci85 Firmware.

## How do I fix CVE-2023-33921?

No fix has been published for CVE-2023-33921 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-33921 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-33921 exists.

## Other vulnerabilities in Siemens CP-8031 MASTER MODULE

- [CVE-2023-33919](https://insights.sbomify.com/CVE-2023-33919/): Command injection in CP-8031 MASTER MODULE (high 7.2)
- [CVE-2023-33920](https://insights.sbomify.com/CVE-2023-33920/): Hardcoded credentials in CP-8031 MASTER MODULE (medium 6.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-33921 and fix it if it is affected.

What it is: CVE-2023-33921 is a medium-severity authentication bypass vulnerability in Siemens CP-8031 MASTER MODULE, published on 13 Jun 2023. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-33921 exists.

Affected product: Siemens CP-8031 MASTER MODULE. 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-2023-33921/ (Markdown: https://insights.sbomify.com/CVE-2023-33921/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-33921
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-33921
- OSV: https://osv.dev/vulnerability/CVE-2023-33921

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From sbomify Insights: https://insights.sbomify.com/CVE-2023-33921/
Summaries are generated and may contain mistakes; the official description above is the record.