Insufficiently Protected Credentials vulnerability in hackney in benoitc hackney allows a redirecting server to obtain the basic_auth and cookie credentials of a request via a same-host redirect to another scheme or port. With follow_redirect enabled, hackney:follow_redirect/10 in src/hackney.erl reissues the request to the Location target after hackney:maybe_strip_auth_on_redirect/3, which compared only the hostname of the current and the redirect URL. A redirect from https to http on the same host resent the Authorization and Cookie headers in cleartext, where an on-path attacker can read them, and a redirect to another port on the same host handed them to a different service. location_trusted forwards credentials to any target by design and is unchanged.
This issue affects hackney: from 2.0.0 before 4.9.0.
The request is made with follow_redirect enabled and the basic_auth or cookie option set, over HTTP/1.1 or HTTP/2, without location_trusted. Credentials passed as explicit request headers are not forwarded on redirects and are not affected.
Disable follow_redirect and handle the Location header in the application, or pass the credentials as explicit Authorization and Cookie request headers instead of the basic_auth and cookie options. hackney:follow_redirect/10 issues the redirected request with an empty header list, so explicit headers reach the first server only.