CVE-2026-55425: Graylog Server: System Catalog titles endpoint can be used to retrieve values of protected database fields

A vulnerability was found in Graylog’s API endpoint for retrieving system catalog entity titles. Authenticated users could retrieve database fields of supported entities by sending a custom API request. These fields can include e.g. the password hash of a user (but not the password itself), which should not be returned through the API, regardless of the endpoint. Permission checks do still apply, so users can retrieve their own password hash, but not those of other users. The admin user (or any user with an admin role) can retrieve password hashes of all users.