Zyxel ATP, USG FLEX, VPN, and ZyWALL/USG firewalls allow for improper error message handling which could allow an unauthenticated attacker to execute OS commands remotely by sending crafted packets to an affected device.

An authentication bypasss vulnerability in the web-based management interface of Zyxel USG/Zywall series firmware versions 4.35 through 4.64 and USG Flex, ATP, and VPN series firmware versions 4.35 through 5.01, which could allow a remote attacker to execute arbitrary commands on an affected device.

ZyXEL ZyWALL USG 2.12 AQQ.2 and 3.30 AQQ.7 devices are affected by a CSRF vulnerability via a cgi-bin/zysh-cgi cmd action to add a user account. This account's access could, for example, subsequently be used for stored XSS.