Gateway: apicast basic auth bypass via malformed base64 headerssending non-base64 'basic' auth with special characters causes apicast to incorrectly authenticate a request

A flaw was found in Gateway. Sending a non-base64 'basic' auth with special characters can cause APICast to incorrectly authenticate a request. A malformed basic authentication header containing special characters bypasses authentication and allows unauthorized access to the backend. This issue can occur due to a failure in the base64 decoding process, which causes APICast to skip the rest of the authentication checks and proceed with routing the request upstream.