authentik is an open-source identity provider. A vulnerability that exists in versions prior to 2024.8.3 and 2024.6.5 allows bypassing password login by adding X-Forwarded-For header with an unparsable IP address, e.g. `a`. This results in a possibility of logging into any account with a known login or email address. The vulnerability requires the authentik instance to trust X-Forwarded-For header provided by the attacker, thus it is not reproducible from external hosts on a properly configured environment. The issue occurs due to the password stage having a policy bound to it, which skips the password stage if the Identification stage is setup to also contain a password stage. Due to the invalid X-Forwarded-For header, which does not get validated to be an IP Address early enough, the exception happens later and the policy fails. The default blueprint doesn't correctly set `failure_result` to `True` on the policy binding meaning that due to this exception the policy returns false and the password stage is skipped. Versions 2024.8.3 and 2024.6.5 fix this issue.
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.