Zyxel security advisory for OS command injection

CVE: CVE-2023-28771


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.



Thanks to TRAPA Security for reporting the issue to us.


Revision history

2023-4-25: Initial release

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