CVE-2023-35138: Zyxel NAS326 Firmware

Critical severity, CVSS 9.8. EPSS: 40% chance of exploitation in the next 30 days.

A command injection vulnerability in the “show_zysync_server_contents” function of the Zyxel NAS326 firmware version V5.21(AAZF.14)C0 and NAS542 firmware version V5.21(ABAG.11)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands by sending a crafted HTTP POST request.

Affected products

• Zyxel NAS326 Firmware: up to and including 5.21\(aazf.14\)c0
• Zyxel NAS542 Firmware: up to and including 5.21\(abag.11\)c0

Published 2023-11-30. Last modified 2026-06-17.