AIOHTTP Affected by Denial of Service (DoS) via Unbounded DNS Cache in TCPConnector

HIGH 7.5CVE-2026-34513 · GHSA-hcc4-c3v8-rx92 · PYSEC-2026-2095 · Published 01/04/2026 · updated 25/10/2026

Package	Affected versions	Patched versions
aiohttp PyPI	`< 3.13.4`	`3.13.4`
aiohttp aiohttp	`< 3.13.4`	`3.13.4`

Description

Summary

An unbounded DNS cache could result in excessive memory usage possibly resulting in a DoS situation.

Impact

If an application makes requests to a very large number of hosts, this could cause the DNS cache to continue growing and slowly use excessive amounts of memory.

Patch: https://github.com/aio-libs/aiohttp/commit/c4d77c3533122be353b8afca8e8675e3b4cbda98

NVD description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, an unbounded DNS cache could result in excessive memory usage possibly resulting in a DoS situation. This issue has been patched in version 3.13.4.

References

aio-libs/aiohttp security advisory · WEB
nvd.nist.gov/vuln/detail/CVE-2026-34513 · ADVISORY
aio-libs/aiohttp commit c4d77c3 · WEB
aio-libs/aiohttp · PACKAGE
aio-libs/aiohttp release v3.13.4 · WEB

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