Impact

A specially crafted Socket.IO packet can trigger an uncaught exception on the Socket.IO server, thus killing the Node.js process.

node:events:502
    throw err; // Unhandled 'error' event
    ^

Error [ERR_UNHANDLED_ERROR]: Unhandled error. (undefined)
    at new NodeError (node:internal/errors:405:5)
    at Socket.emit (node:events:500:17)
    at /myapp/node_modules/socket.io/lib/socket.js:531:14
    at process.processTicksAndRejections (node:internal/process/task_queues:77:11) {
  code: 'ERR_UNHANDLED_ERROR',
  context: undefined
}

Affected versions

Patches

This issue is fixed by socketio/socket.io@15af22f, included in socket.io@4.6.2 (released in May 2023).

The fix was backported in the 2.x branch today: socketio/socket.io@d30630b

Workarounds

As a workaround for the affected versions of the socket.io package, you can attach a listener for the "error" event:

io.on("connection", (socket) => {
  socket.on("error", () => {
    // ...
  });
});

For more information

If you have any questions or comments about this advisory:

• Open a discussion here

Thanks a lot to Paul Taylor for the responsible disclosure.

References

• socketio/socket.io@15af22f
• socketio/socket.io@d30630b

References

• GHSA-25hc-qcg6-38wj
• socketio/socket.io@15af22f
• socketio/socket.io@d30630b
• https://nvd.nist.gov/vuln/detail/CVE-2024-38355