ZyXel Prestige 642R Router WAN Port Filter Bypass Vulnerability

ZyXel Prestige 642R Router WAN Port Filter Bypass Vulnerability

ZyXel Prestige Routers allow administrators to filter ports on both the WAN and LAN interfaces. By default, the filters are set to block WAN IP addresses access to the Telnet administration interface on TCP port 23, and FTP access on TCP port 21.

An administrator can also set up a filter on the LAN interface in order to block internal network users from accessing these administration interfaces.

The WAN interface does not filter internal IP addresses from these ports, however, allowing an internal attacker to access the administration interface by connecting to the router's WAN IP address.