CVE-2026-33495: Ory Oathkeeper has an authentication bypass by usage of untrusted header

Ory Oathkeeper is often deployed behind other components like CDNs, WAFs, or reverse proxies. Depending on the setup, another component might forward the request to the Oathkeeper proxy with a different protocol (http vs. https) than the original request. In order to properly match the request against the configured rules, Oathkeeper considers the X-Forwarded-Proto header when evaluating rules. The configuration option serve.proxy.trust_forwarded_headers (defaults to false) governs whether this and other X-Forwarded-* headers should be trusted. Oathkeeper did not properly respect this configuration, and would always consider the X-Forwarded-Proto header.