CVE-2026-48809: python-engineio has possible denial of service due to maximum payload size sometimes not being enforced

There are two specific configurations of the python-engineio server in which the size of incoming messages is not checked before the messages are loaded into memory. An attacker can take advantage of these to cause unnecessary memory allocations in the python-engineio server. The two cases are:

• POST requests, when using ASGI with the long polling transport
• WebSocket messages, when using Aiohttp with the WebSocket transport