AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.12.14, the Python parser is vulnerable to a request smuggling vulnerability due to not parsing trailer sections of an HTTP request. If a pure Python version of aiohttp is installed (i.e. without the usual C extensions) or AIOHTTP_NO_EXTENSIONS is enabled, then an attacker may be able to execute a request smuggling attack to bypass certain firewalls or proxy protections. Version 3.12.14 contains a patch for this issue.

Affected versions of aiohttp are vulnerable to HTTP Request Smuggling (CWE-444). This vulnerability allows attackers to inject malicious HTTP messages by including line feeds (LF) in chunk extensions, potentially bypassing security controls and executing unauthorized actions. The attack vector involves sending specially crafted chunked HTTP requests to exploit the improper parsing in the HttpPayloadParser class. To mitigate, upgrade to aiohttp version which validates chunk extensions by rejecting any containing unexpected LFs, thereby preventing request smuggling attacks.

Affected versions of aiohttp are vulnerable to Middleware Cache Pollution. This vulnerability allows attackers to potentially interfere with middleware handling by exploiting cached middleware associated with system routes. The impact includes possible bypassing of security middleware or unintended access to internal routes. The attack vector involves crafting requests that target system routes, causing the middleware cache to store and reuse inappropriate middleware configurations. The vulnerable methods are _build_middlewares and the middleware caching mechanism in web_app.py. To mitigate, upgrade to aiohttp version, which prevents system routes from polluting the middleware cache by excluding SystemRoute instances from caching.