Uncaught Exception in engine.io

Impact

A specially crafted HTTP request can trigger an uncaught exception on the Engine.IO server, thus killing the Node.js process.

> RangeError: Invalid WebSocket frame: RSV2 and RSV3 must be clear
> at Receiver.getInfo (/…/node_modules/ws/lib/receiver.js:176:14)
> at Receiver.startLoop (/…/node_modules/ws/lib/receiver.js:136:22)
> at Receiver._write (/…/node_modules/ws/lib/receiver.js:83:10)
> at writeOrBuffer (internal/streams/writable.js:358:12)

This impacts all the users of the engine.io package starting from version 4.0.0, including those who uses depending packages like socket.io.

Patches

A fix has been released for each major branch:

Previous versions (< 4.0.0) are not impacted.

For socket.io users:

In most cases, running npm audit fix should be sufficient. You can also use npm update engine.io --depth=9999.

Workarounds

There is no known workaround except upgrading to a safe version.

For more information

If you have any questions or comments about this advisory:

• Open an issue in engine.io

Thanks to Marcus Wejderot from Mevisio for the responsible disclosure.