Zyxel security advisory for pre-authentication command injection vulnerability in NAS products

CVE: CVE-2023-27992

Zyxel has released patches addressing a pre-authentication command injection vulnerability in some NAS versions. Users are advised to install them for optimal protection.

What is the vulnerability?

The pre-authentication command injection vulnerability in some Zyxel NAS devices could allow an unauthenticated attacker to execute some operating system (OS) commands remotely by sending a crafted HTTP request.

What versions are vulnerable—and what should you do?

After a thorough investigation, we have identified the vulnerable products that are within their vulnerability support period, with their firmware patches shown in the table below.

Affected model Affected version Patch availability
NAS326 V5.21(AAZF.13)C0 and earlier V5.21(AAZF.14)C0
NAS540 V5.21(AATB.10)C0 and earlier V5.21(AATB.11)C0
NAS542 V5.21(ABAG.10)C0 and earlier V5.21(ABAG.11)C0
Got a question?

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


Thanks to Andrej Zaujec, NCSC-FI, and Maxim Suslov for reporting the issue to us.

Revision history

2023-6-20: Initial release.