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:

Version range	Fixed version
engine.io@4.x.x	4.1.2
engine.io@5.x.x	5.2.1
engine.io@6.x.x	6.1.1

Previous versions (< 4.0.0) are not impacted.

For socket.io users:

Version range	engine.io version	Needs minor update?
socket.io@4.4.x	~6.1.0	-
socket.io@4.3.x	~6.0.0	Please upgrade to socket.io@4.4.x
socket.io@4.2.x	~5.2.0	-
socket.io@4.1.x	~5.1.1	Please upgrade to socket.io@4.4.x
socket.io@4.0.x	~5.0.0	Please upgrade to socket.io@4.4.x
socket.io@3.1.x	~4.1.0	-
socket.io@3.0.x	~4.0.0	Please upgrade to socket.io@3.1.x or socket.io@4.4.x (see here)

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.