CVE-2026-34517

Summary

For some multipart form fields, aiohttp read the entire field into memory before checking client_max_size.

Impact

If an application uses Request.post() an attacker can send a specially crafted multipart request to force significant temporary memory allocation even when the request is ultimately rejected.

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Patch: https://github.com/aio-libs/aiohttp/commit/cbb774f38330563422ca0c413a71021d7b944145