# CVE-2021-40084: Command injection in n/a

> opensysusers allows command execution via shell metacharacters in GECOS fields due to unsafe eval usage, requiring a patch to prevent privilege escalation.

- **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:** Yes
- **Published:** 25 Aug 2021
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-40084, GHSA-2hgh-26fm-566h, UBUNTU-CVE-2021-40084

## What is CVE-2021-40084?

CVE-2021-40084 is a critical command injection vulnerability in n/a, published on 25 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

opensysusers through 0.6 does not safely use eval on files in sysusers.d that may contain shell metacharacters. For example, it allows command execution via a crafted GECOS field whereas systemd-sysusers (a program with the same specification) does not do that.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2021-40084?

It affects 1 product.


Products: Artixlinux Opensysusers.

## How do I fix CVE-2021-40084?

Apply the vendor's patch.

## Is CVE-2021-40084 being exploited?

There is no known exploitation of CVE-2021-40084 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-40084 and fix it if it is affected.

What it is: CVE-2021-40084 is a critical command injection vulnerability in n/a, published on 25 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-2021-40084 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-2021-40084/ (Markdown: https://insights.sbomify.com/CVE-2021-40084/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-40084
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-40084
- OSV: https://osv.dev/vulnerability/CVE-2021-40084

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-40084/
Summaries are generated and may contain mistakes; the official description above is the record.