# CVE-2023-28771: Zyxel Multiple Firewalls OS Command Injection

> Unauthenticated attackers can execute OS commands on Zyxel firewalls via crafted packets due to improper error handling.

- **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:** Yes, since 31 May 2023 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Apr 2023
- **Updated:** 21 Oct 2025
- **Also known as:** GHSA-3xvp-8qg2-x43w

## What is CVE-2023-28771?

CVE-2023-28771 is a critical command injection vulnerability in Zyxel ATP series firmware, published on 25 Apr 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Improper error message handling in Zyxel ZyWALL/USG series firmware versions 4.60 through 4.73, VPN series firmware versions 4.60 through 5.35, USG FLEX series firmware versions 4.60 through 5.35, and ATP series firmware versions 4.60 through 5.35, which could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.

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

## Which versions are affected by CVE-2023-28771?

It affects 19 products.


Products: Zyxel Atp100 Firmware, Zyxel Atp100w Firmware, Zyxel Atp200 Firmware, Zyxel Atp500 Firmware, Zyxel Atp700 Firmware, Zyxel Atp800 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, Zyxel Zywall Usg 100 Firmware, Zyxel Zywall Usg 310 Firmware.

## How do I fix CVE-2023-28771?

No fix has been published for CVE-2023-28771 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 21 Jun 2023.

## Is CVE-2023-28771 being exploited?

Yes. Attackers have exploited CVE-2023-28771 in the wild since at least 31 May 2023.

Public exploit code:

- PoC for CVE-2023-28771 based on Rapid7's excellent writeup (github_poc): https://github.com/benjaminhays/CVE-2023-28771-PoC
- Zyxel IKE Packet Decoder Unauthenticated Remote Code Execution (metasploit)
- https://github.com/JinParkmida/cve-2023-28771-demo (github_poc): https://github.com/JinParkmida/cve-2023-28771-demo

## 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-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)
- [CVE-2020-9054](https://insights.sbomify.com/CVE-2020-9054/): Zyxel Multiple NAS Devices OS Command Injection (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-28771 and fix it if it is affected.

What it is: CVE-2023-28771 is a critical command injection vulnerability in Zyxel ATP series firmware, published on 25 Apr 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2023-28771 in the wild since at least 31 May 2023.

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-2023-28771/ (Markdown: https://insights.sbomify.com/CVE-2023-28771/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-28771
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-28771
- OSV: https://osv.dev/vulnerability/CVE-2023-28771

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-28771/
Summaries are generated and may contain mistakes; the official description above is the record.