AIOHTTP leaks Cookie and Proxy-Authorization headers on cross-origin redirect

MEDIUM 5.3CVE-2026-34518 · GHSA-966j-vmvw-g2g9 · PYSEC-2026-2100 · Published 01/04/2026 · updated 26/10/2026

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

Description

Summary

When following redirects to a different origin, aiohttp drops the Authorization header, but retains the Cookie and Proxy-Authorization headers.

Impact

The Cookie and Proxy-Authorizations headers could contain sensitive information which may be leaked to an unintended party after following a redirect.

Patch: https://github.com/aio-libs/aiohttp/commit/5351c980dcec7ad385730efdf4e1f4338b24fdb6

NVD description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, when following redirects to a different origin, aiohttp drops the Authorization header, but retains the Cookie and Proxy-Authorization headers. This issue has been patched in version 3.13.4.

References

aio-libs/aiohttp security advisory · WEB
nvd.nist.gov/vuln/detail/CVE-2026-34518 · ADVISORY
aio-libs/aiohttp commit 5351c98 · WEB
aio-libs/aiohttp · PACKAGE
aio-libs/aiohttp release v3.13.4 · WEB

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