Engine.IO is the implementation of transport-based cross-browser/cross-device bi-directional communication layer for Socket.IO. A specially crafted HTTP request can trigger an uncaught exception on the Engine.IO server, thus killing the Node.js process. This impacts all the users of the engine.io package, including those who uses depending packages like socket.io. There is no known workaround except upgrading to a safe version. This issue affects versions prior to 3.6.1, and 4.0.x prior to 6.2.1.
CWE-248 - Uncaught Exception
An exception is thrown from a function, but it is not caught.