The attacker can use the raft server protocol in an unauthenticated way. The attacker can see the server's resources, including directories and files. This issue affects Apache Zeppelin: from 0.10.1 up to 0.12.0. Users are recommended to upgrade to version 0.12.0, which fixes the issue by removing the Cluster Interpreter.
https://lists.apache.org/thread/moyym04993c8owh4h0qj98r43tbo8qdd