CVE-2026-34517AIOHTTP: Late size enforcement for non-file multipart fields causes memory DoS

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, for some multipart form fields, aiohttp read the entire field into memory before checking client_max_size. This issue has been patched in version 3.13.4.

Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.

Affected products and versions

References and patches

• https://github.com/aio-libs/aiohttp/security/advisories/GHSA-3wq7-rqq7-wx6j PatchVendor Advisory
• https://github.com/aio-libs/aiohttp/commit/cbb774f38330563422ca0c413a71021d7b944145 Patch
• https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4 Release Notes