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python · python-engineioCritical

python-engineio: Unchecked message size in ASGI long polling and Aiohttp WebSocket

In python-engineio, incoming message size is not checked before loading into memory for POST requests with ASGI long polling transport and WebSocket messages with Aiohttp WebSocket transport.

27 Jun 2026Read 1 minSeverity: act now

What changed

In python-engineio, incoming message size is not checked before loading into memory for POST requests with ASGI long polling transport and WebSocket messages with Aiohttp WebSocket transport. Version 4.13.2 patches this by discarding oversized or unauthenticated requests in ASGI and configuring max payload size in Aiohttp WebSocket layer.

Who it affects

Users of python-engineio server with ASGI long polling transport or Aiohttp WebSocket transport.

What to do today

Upgrade python-engineio to version 4.13.2 or later.

The trail
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