engine.io Uncaught Exception vulnerability

Impact

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

TypeError: Cannot read properties of undefined (reading 'handlesUpgrades')
    at Server.onWebSocket (build/server.js:515:67)

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

Patches

A fix has been released today (2023/05/02): 6.4.2

This bug was introduced in version 5.1.0 and included in version 4.1.0 of the socket.io parent package. Older versions are not impacted.

For socket.io users:

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 Thomas Rinsma from Codean for the responsible disclosure.