socket.io has an unhandled 'error' event
### 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
| Version range | Needs minor update? |
|------------------|------------------------------------------------|
| `4.6.2...latest` | Nothing to do |
| `3.0.0...4.6.1` | Please upgrade to `socket.io@4.6.2` (at least) |
| `2.3.0...2.5.0` | Please upgrade to `socket.io@2.5.1` |
### Patches
This issue is fixed by
https://github.com/socketio/socket.io/commit/15af22fc22bc6030fcead322c106f07640336115, included in `socket.io@4.6.2` (released in May 2023).
The fix was backported in the 2.x branch today:
https://github.com/socketio/socket.io/commit/d30630ba10562bf987f4d2b42440fc41a828119c
### Workarounds
As a workaround for the affected versions of the `socket.io` package, you can attach a listener for the "error" event:
```js
io.on("connection", (socket) => {
socket.on("error", () => {
// ...
});
});
```
### For more information
If you have any questions or comments about this advisory:
- Open a discussion here
https://github.com/socketio/socket.io/discussions
Thanks a lot to Paul Taylor
https://github.com/Y0ursTruly for the responsible disclosure.
### References
-
https://github.com/socketio/socket.io/commit/15af22fc22bc6030fcead322c106f07640336115
-
https://github.com/socketio/socket.io/commit/d30630ba10562bf987f4d2b42440fc41a828119c