# CVE-2021-25674: Null dereference in SIMATIC S7-PLCSIM V5.4

> A local attacker can cause a denial of service in SIMATIC S7-PLCSIM by opening a specially crafted file, triggering a null pointer dereference.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Mar 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-jg4g-p5jg-phcr

## What is CVE-2021-25674?

CVE-2021-25674 is a medium-severity vulnerability in Siemens SIMATIC S7-PLCSIM V5.4, published on 15 Mar 2021. 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 SIMATIC S7-PLCSIM V5.4 (All versions). An attacker with local access to the system could cause a Denial-of-Service condition in the application when it is used to open a specially crafted file. As a consequence, a NULL pointer deference condition could cause the application to terminate unexpectedly and must be restarted to restore the service.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2021-25674?

It affects 1 product.


Products: Siemens Simatic S7-Plcsim.

## How do I fix CVE-2021-25674?

No fix has been published for CVE-2021-25674 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-25674 being exploited?

There is no known exploitation of CVE-2021-25674 in the wild and no public exploit code.

## Other vulnerabilities in Siemens SIMATIC S7-PLCSIM V5.4

- [CVE-2021-25673](https://insights.sbomify.com/CVE-2021-25673/): Denial of service in SIMATIC S7-PLCSIM V5.4 (medium 5.5)
- [CVE-2021-25675](https://insights.sbomify.com/CVE-2021-25675/): Denial of service in SIMATIC S7-PLCSIM V5.4 (medium 5.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-25674 and fix it if it is affected.

What it is: CVE-2021-25674 is a medium-severity vulnerability in Siemens SIMATIC S7-PLCSIM V5.4, published on 15 Mar 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-25674 in the wild and no public exploit code.

Affected product: Siemens SIMATIC S7-PLCSIM V5.4. 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-2021-25674/ (Markdown: https://insights.sbomify.com/CVE-2021-25674/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-25674
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-25674
- OSV: https://osv.dev/vulnerability/CVE-2021-25674

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-25674/
Summaries are generated and may contain mistakes; the official description above is the record.