Zyxel security advisory for OS command injection vulnerability of firewalls

Zyxel_May · April 2023

CVE: CVE-2023-28771

Summary

Zyxel has released patches for an OS command injection vulnerability found by TRAPA Security and urges users to install them for optimal protection.

What is the vulnerability?

Improper error message handling in some firewall versions could allow an unauthenticated attacker to execute some OS commands remotely by sending crafted packets to an affected device.

What versions are vulnerable—and what should you do?

After a thorough investigation, we’ve identified the vulnerable products that are within their vulnerability support period and released patches to address the vulnerability, as shown in the table below.

Affected series	Affected version	Patch availability
ATP	ZLD V4.60 to V5.35	ZLD V5.36
USG FLEX	ZLD V4.60 to V5.35	ZLD V5.36
VPN	ZLD V4.60 to V5.35	ZLD V5.36
ZyWALL/USG	ZLD V4.60 to V4.73	ZLD V4.73 Patch 1

Got a question?

Please contact your local service rep or visit Zyxel’s forum for further information or assistance.

Acknowledgment

Thanks to TRAPA Security for reporting the issue to us.

Revision history

2023-4-25: Initial release

Anonomous · July 2023

There is no download link for the patch. I am getting repeatedly hit with attack zyxel command injection - CVE-2023-28771 on udp port 500. I NEED THE PATCH!