# CVE-2021-42071: Command injection in n/a

> Unauthenticated attackers can execute arbitrary commands on Visual Tools DVR devices by injecting shell metacharacters into the User-Agent header.

- **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:** No
- **Published:** 7 Oct 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-5pjx-33j8-9h49

## What is CVE-2021-42071?

CVE-2021-42071 is a critical command injection vulnerability in n/a, published on 7 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In Visual Tools DVR VX16 4.2.28.0, an unauthenticated attacker can achieve remote command execution via shell metacharacters in the cgi-bin/slogin/login.py User-Agent HTTP header.

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

## Which versions are affected by CVE-2021-42071?

It affects 1 product.


Products: Visual-Tools Dvr Vx16 Firmware.

## How do I fix CVE-2021-42071?

No fix has been published for CVE-2021-42071 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-42071 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-42071 exists.

Public exploit code:

- Visual Tools DVR VX16 4.2.28.0 - OS Command Injection (Unauthenticated) (exploitdb)
- Visual Tools DVR VX16 4.2.28.0 - Unauthenticated OS Command Injection (nuclei): http/cves/2021/CVE-2021-42071.yaml

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-42071 and fix it if it is affected.

What it is: CVE-2021-42071 is a critical command injection vulnerability in n/a, published on 7 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-42071 exists.

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-2021-42071/ (Markdown: https://insights.sbomify.com/CVE-2021-42071/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-42071
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-42071
- OSV: https://osv.dev/vulnerability/CVE-2021-42071

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-42071/
Summaries are generated and may contain mistakes; the official description above is the record.