Socket.io is a realtime application framework that provides communication via websockets. Because socket.io 0.9.6 and earlier depends on Math.random() to create socket IDs, the IDs are predictable. An attacker is able to guess the socket ID and gain access to socket.io servers, potentially obtaining sensitive information.

The package socket.io before 2.4.0 are vulnerable to Insecure Defaults due to CORS Misconfiguration. All domains are whitelisted by default.