# CVE-2021-37172: Auth bypass in SIMATIC S7-1200 CPU family (incl. SIPLUS variants)

> Attackers can bypass authentication to download arbitrary programs to SIMATIC S7-1200 PLCs if provisioned with TIA Portal V13.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Aug 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-jx4h-7jg8-gqhf

## What is CVE-2021-37172?

CVE-2021-37172 is a high-severity authentication bypass vulnerability in Siemens SIMATIC S7-1200 CPU family (incl. SIPLUS variants), published on 10 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability has been identified in SIMATIC S7-1200 CPU family (incl. SIPLUS variants) (V4.5.0). Affected devices fail to authenticate against configured passwords when provisioned using TIA Portal V13. This could allow an attacker using TIA Portal V13 or later versions to bypass authentication and download arbitrary programs to the PLC. The vulnerability does not occur when TIA Portal V13 SP1 or any later version was used to provision the device.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2021-37172?

It affects 2 products.


Products: Siemens Simatic S7-1200 Cpu Firmware, Siemens Simatic Step 7 \(Tia Portal\).

## How do I fix CVE-2021-37172?

No fix has been published for CVE-2021-37172 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-37172 being exploited?

There is no known exploitation of CVE-2021-37172 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-37172 and fix it if it is affected.

What it is: CVE-2021-37172 is a high-severity authentication bypass vulnerability in Siemens SIMATIC S7-1200 CPU family (incl. SIPLUS variants), published on 10 Aug 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-2021-37172 in the wild and no public exploit code.

Affected product: Siemens SIMATIC S7-1200 CPU family (incl. SIPLUS variants). 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-2021-37172/ (Markdown: https://insights.sbomify.com/CVE-2021-37172/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-37172
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-37172
- OSV: https://osv.dev/vulnerability/CVE-2021-37172

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-37172/
Summaries are generated and may contain mistakes; the official description above is the record.