CVE-2026-34518

Affected versions of the aiohttp package are vulnerable to Information Disclosure due to improper handling of sensitive headers during cross-origin redirects. When following a redirect to a different origin, the library correctly strips the Authorization header but fails to remove the Cookie and Proxy-Authorization headers, allowing them to be forwarded to the unintended destination. An attacker controlling or observing the redirect target can capture these leaked credentials and session tokens, potentially gaining unauthorised access to user accounts or upstream proxies.