### SummaryImproper validation make it possible for an attacker to modify the HTTP request (e.g. to insert a new header) or even create a new HTTP request if the attacker controls the HTTP version.### DetailsThe vulnerability only occurs if the attacker can control the HTTP version of the request (including its type).For example if an unvalidated JSON value is used as a version and the attacker is then able to pass an array as the `version` parameter.Furthermore, the vulnerability only occurs when the `Connection` header is passed to the `headers` parameter.At this point, the library will use the parsed value to create the request. If a list is passed, then it bypasses validation and it is possible to perform CRLF injection.### PoCThe POC below shows an example of providing an unvalidated array as a version:https://gist.github.com/jnovikov/184afb593d9c2114d77f508e0ccd508e### ImpactCRLF injection leading to Request Smuggling.### WorkaroundIf these specific conditions are met and you are unable to upgrade, then validate the user input to the `version` parameter to ensure it is a `str`.Patch: https://github.com/aio-libs/aiohttp/pull/7835/files