PYSEC-2026-3042

### Impact The python-socketio server stores binary `EVENT` and `ACK` messages in memory while it waits to receive their binary attachments. Once all the attachments are received, these messages are then processed. An attacker can submit a binary message and intentionally omit sending one or more of its attachments to cause the message along with the partial list of received attachments to stay in memory for a long time.

### Patches Version 5.16.2 takes the following measures to address this issue: - Binary packets are only accepted from authenticated clients. - When a client disconnects, the server checks if there is a partial binary message being held for the client and deletes it.