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

Source: https://junglewise.ai/threats/cve-2023-28771-zyxel-multiple-firewalls-os-command-injection-vulnerability  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2023-05-31. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2023-28771 · Severity: critical · CVSS 9.8 · Exploited in the wild · Published 2023-05-31

Improper error message handling in multiple Zyxel firewall series allows an unauthenticated remote attacker to execute OS commands by sending crafted packets to the device. The vulnerability stems from a flaw in the IKE packet decoder.

Technologies: [Zyxel Firewalls](https://junglewise.ai/threats/technologies/firewalls), [Zyxel Multiple Firewalls](https://junglewise.ai/threats/technologies/multiple-firewalls). Vendors: [Zyxel](https://junglewise.ai/threats/vendors/zyxel).

## Quick answers

**Is CVE-2023-28771 exploited in the wild?** Yes. CVE-2023-28771 is known to be exploited in the wild, first recorded on 31 May 2023. Treat it as urgent.

**How severe is CVE-2023-28771?** Critical severity, with a CVSS score of 9.8, published 31 May 2023.

**Which products and versions are affected?** Zyxel ATP series firmware 4.60 through 5.35; Zyxel USG FLEX series firmware 4.60 through 5.35; Zyxel VPN series firmware 4.60 through 5.35; Zyxel ZyWALL/USG series firmware 4.60 through 4.73.

**Is there a fix for CVE-2023-28771?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2023-28771 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2023-28771?** Check whether you run Zyxel Firewalls or Zyxel Multiple Firewalls. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Zyxel ATP series firmware 4.60 through 5.35
- Zyxel USG FLEX series firmware 4.60 through 5.35
- Zyxel VPN series firmware 4.60 through 5.35
- Zyxel ZyWALL/USG series firmware 4.60 through 4.73

## Timeline

- 2023-05-31: disclosed: Vulnerability published and added to CISA KEV catalog
- 2023-05-31: kev added
- 2023-05-31: exploited: Reported as exploited in the wild at time of publication

## Related threats

- [Zyxel Multiple Firewalls Path Traversal Vulnerability](https://junglewise.ai/threats/cve-2024-11667-zyxel-multiple-firewalls-path-traversal-vulnerability)
- [Zyxel Multiple Firewalls Buffer Overflow Vulnerability](https://junglewise.ai/threats/cve-2023-33010-zyxel-multiple-firewalls-buffer-overflow-vulnerability)
- [Zyxel Multiple Firewalls Buffer Overflow Vulnerability](https://junglewise.ai/threats/cve-2023-33009-zyxel-multiple-firewalls-buffer-overflow-vulnerability)
- [Zyxel Multiple Firewalls OS Command Injection Vulnerability](https://junglewise.ai/threats/cve-2022-30525-zyxel-multiple-firewalls-os-command-injection-vulnerability)