The locally served web site on the Garmin WDU (v1 1.4.6 and v2 5.0) allows a cross-site origin WebSocket hijacking attack. Among other uses, the WDU utilizes WebSockets to control settings, including administrative settings. This allows a network attacker to take full control of a WDU. To initiate an exploit of this vulnerability, the victim must (1) be utilizing a web browser on a multihomed host that has local interfaces on the Garmin Marine Network as well as another network, and (2) access a malicious third party website created by the attacker.