# CVE-2021-4039: Command injection in NWA1100-NH firmware

> An attacker can execute arbitrary OS commands on the Zyxel NWA-1100-NH via its web interface, requiring a firmware patch.

- **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:** 1 Mar 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-9ww2-qwrq-m7wv

## What is CVE-2021-4039?

CVE-2021-4039 is a critical command injection vulnerability in Zyxel NWA1100-NH firmware, published on 1 Mar 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A command injection vulnerability in the web interface of the Zyxel NWA-1100-NH firmware could allow an attacker to execute arbitrary OS commands on the device.

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

## Which versions are affected by CVE-2021-4039?

It affects 1 product.


Products: Zyxel Nwa1100-Nh Firmware.

## How do I fix CVE-2021-4039?

No fix has been published for CVE-2021-4039 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-4039 being exploited?

There is no known exploitation of CVE-2021-4039 in the wild and no public exploit code.

Public exploit code:

- Zyxel NWA-1100-NH - Command Injection (exploitdb)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-4039 and fix it if it is affected.

What it is: CVE-2021-4039 is a critical command injection vulnerability in Zyxel NWA1100-NH firmware, published on 1 Mar 2022. 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-2021-4039 in the wild and no public exploit code.

Affected product: Zyxel NWA1100-NH firmware. 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-2021-4039/ (Markdown: https://insights.sbomify.com/CVE-2021-4039/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-4039
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-4039
- OSV: https://osv.dev/vulnerability/CVE-2021-4039

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-4039/
Summaries are generated and may contain mistakes; the official description above is the record.