CVE-2026-34518: AIOHTTP leaks Cookie and Proxy-Authorization headers on cross-origin redirect

Executive brief

### 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

Affected products

• PyPI aiohttp

References

• https://api.github.com/users/uug4na
• https://github.com/uug4na
• https://api.github.com/users/uug4na/gists%7B/gist_id%7D
• https://api.github.com/users/uug4na/repos
• https://avatars.githubusercontent.com/u/65070195?v=4
• https://api.github.com/users/uug4na/events%7B/privacy%7D