# CVE-2026-121931: Linksys WRT54GL Traceroute Diagnostic Function apply.cgi system os command injection


- **Severity:** Critical 9.4 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 4 Nov 2026
- **Updated:** 9 Nov 2026
- **Also known as:** GHSA-7p5v-44wr-v953

## What is CVE-2026-121931?

CVE-2026-121931 is a critical vulnerability in Linksys WRT54GL, published on 4 Nov 2026. 

### Official description

A security vulnerability has been detected in Linksys WRT54GL 4.30.18. The impacted element is the function system of the file apply.cgi of the component Traceroute Diagnostic Function. Such manipulation of the argument traceroute_ip leads to os command injection. The attack can be launched remotely. The exploit has been disclosed publicly and may be used. The vendor was contacted early about this disclosure but did not respond in any way. This vulnerability only affects products that are no longer supported by the maintainer.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command), CWE-77 (Improper Neutralization of Special Elements used in a Command)

## Which versions are affected by CVE-2026-121931?


## How do I fix CVE-2026-121931?

No fix has been published for CVE-2026-121931 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-121931 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-121931 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-121931 and fix it if it is affected.

What it is: CVE-2026-121931 is a critical vulnerability in Linksys WRT54GL, published on 4 Nov 2026. 
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-121931 exists.

Affected product: Linksys WRT54GL. 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-2026-121931/ (Markdown: https://insights.sbomify.com/CVE-2026-121931/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-121931
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121931
- OSV: https://osv.dev/vulnerability/CVE-2026-121931

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-121931/
Summaries are generated and may contain mistakes; the official description above is the record.