Zyxel ATP and USG FLEX Series Command Injection Vulnerability in DDNS Configuration

A post-authentication command injection vulnerability has been identified in the Dynamic DNS (DDNS) configuration command-line interface (CLI) for Zyxel ATP series, USG FLEX series, USG FLEX 50(W) series, and USG20(W)-VPN series. All these series are running firmware versions from V5.35 to V5.41. This vulnerability allows an authenticated attacker with administrator privileges to execute operating system commands on the affected device by sending a specially crafted string as an argument to the CLI command.

Impact

Exploitation of this vulnerability could lead to unauthorized execution of operating system commands on the affected device.

Remediation

Users are advised to update to Zyxel ZLD V5.42, which addresses this vulnerability. Instructions for downloading the update can be found on the Zyxel Download Library.