aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. The HTTP parser in AIOHTTP has numerous problems with header parsing, which could lead to request smuggling. This parser is only used when AIOHTTPNOEXTENSIONS is enabled (or not using a prebuilt wheel). These bugs have been addressed in commit
d5c12ba89 which has been included in release version 3.8.6. Users are advised to upgrade. There are no known workarounds for these issues.