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CVE-2024-52303 — aiohttp memory leak when middleware is enabled when requesting a resource with a non-allowed method

2026-09-28T22:57:34.280909+00:00

Affected: aio-libs aiohttp, aiohttp aio-libs

aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. In versions starting with 3.10.6 and prior to 3.10.11, a memory leak can occur when a request produces a MatchInfoError. This was caused by adding an entry to a cache on each request, due to the building of each MatchInfoError producing a unique cache entry. An attacker may be able to exhaust the memory resources of a server by sending a substantial number (100,000s to millions) of such requests. Those who use any middlewares with aiohttp.web should upgrade to version 3.10.11 to receive a patch.

GHSA-27mf-ghqm-j3j8 — aiohttp has a memory leak when middleware is enabled when requesting a resource with a non-allowed method

2026-09-28T22:57:34.281179+00:00

Affected: PyPI: aiohttp

### Summary

A memory leak can occur when a request produces a `MatchInfoError`. This was caused by adding an entry to a cache on each request, due to the building of each `MatchInfoError` producing a unique cache entry.

### Impact

If the user is making use of any middlewares with `aiohttp.web` then it is advisable to upgrade immediately.

An attacker may be able to exhaust the memory resources of a server by sending a substantial number (100,000s to millions) of such requests.

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Patch: https://github.com/aio-libs/aiohttp/commit/bc15db61615079d1b6327ba42c682f758fa96936

PYSEC-2026-1096 — aiohttp has a memory leak when middleware is enabled when requesting a resource with a non-allowed method