# CVE-2023-27991: Command injection in ATP series firmware

> An authenticated attacker can execute arbitrary OS commands remotely via the CLI in Zyxel firewall firmware.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Apr 2023
- **Updated:** 4 Feb 2025
- **Also known as:** GHSA-2j4f-52m8-xq9h

## What is CVE-2023-27991?

CVE-2023-27991 is a high-severity command injection vulnerability in Zyxel ATP series firmware, published on 24 Apr 2023. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The post-authentication command injection vulnerability in the CLI command of Zyxel ATP series firmware versions 4.32 through 5.35, USG FLEX series firmware versions 4.50 through 5.35, USG FLEX 50(W) firmware versions 4.16 through 5.35, USG20(W)-VPN firmware versions 4.16 through 5.35, and VPN series firmware versions 4.30 through 5.35, which could allow an authenticated attacker to execute some OS commands remotely.

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

## Which versions are affected by CVE-2023-27991?

It affects 19 products.


Products: Zyxel Atp100 Firmware, Zyxel Atp100w Firmware, Zyxel Atp200 Firmware, Zyxel Atp500 Firmware, Zyxel Atp700 Firmware, Zyxel Atp800 Firmware, Zyxel Usg20-Vpn Firmware, Zyxel Usg 20w-Vpn Firmware, Zyxel Usg Flex 100 Firmware, Zyxel Usg Flex 100w Firmware, Zyxel Usg Flex 200 Firmware, Zyxel Usg Flex 500 Firmware, Zyxel Usg Flex 50 Firmware, Zyxel Usg Flex 50w Firmware, Zyxel Usg Flex 700 Firmware, Zyxel Vpn1000 Firmware, Zyxel Vpn100 Firmware, Zyxel Vpn300 Firmware, Zyxel Vpn50 Firmware.

## How do I fix CVE-2023-27991?

No fix has been published for CVE-2023-27991 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-27991 being exploited?

There is no known exploitation of CVE-2023-27991 in the wild and no public exploit code.

## Other vulnerabilities in Zyxel ATP series firmware

- [CVE-2023-33009](https://insights.sbomify.com/CVE-2023-33009/): Zyxel Multiple Firewalls Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2023-33010](https://insights.sbomify.com/CVE-2023-33010/): Zyxel Multiple Firewalls Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2023-28771](https://insights.sbomify.com/CVE-2023-28771/): Zyxel Multiple Firewalls OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2022-30525](https://insights.sbomify.com/CVE-2022-30525/): Zyxel Multiple Firewalls OS Command Injection (critical 9.8, exploited in the wild)
- [CVE-2020-29583](https://insights.sbomify.com/CVE-2020-29583/): Zyxel Multiple Products Use of Hard-Coded Credentials (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-27991 and fix it if it is affected.

What it is: CVE-2023-27991 is a high-severity command injection vulnerability in Zyxel ATP series firmware, published on 24 Apr 2023. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-27991 in the wild and no public exploit code.

Affected product: Zyxel ATP series 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-2023-27991/ (Markdown: https://insights.sbomify.com/CVE-2023-27991/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-27991
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-27991
- OSV: https://osv.dev/vulnerability/CVE-2023-27991

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-27991/
Summaries are generated and may contain mistakes; the official description above is the record.