LOW

GHSA-3wq7-rqq7-wx6j

AIOHTTP has late size enforcement for non-file multipart fields causes memory DoS

Details

### 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

Are you affected?

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Affected packages

PyPI / aiohttp

Introduced in: 0 Fixed in: 3.13.4

Fix pip install --upgrade 'aiohttp>=3.13.4'

References

https://github.com/aio-libs/aiohttp/security/advisories/GHSA-3wq7-rqq7-wx6j [WEB]
https://nvd.nist.gov/vuln/detail/CVE-2026-34517 [ADVISORY]
https://github.com/aio-libs/aiohttp/commit/cbb774f38330563422ca0c413a71021d7b944145 [WEB]
https://github.com/aio-libs/aiohttp [PACKAGE]
https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4 [WEB]