The RPC protocol implementation in Apache Hadoop 2.x before 2.0.6-alpha, 0.23.x before 0.23.9, and 1.x before 1.2.1, when the Kerberos security features are enabled, allows man-in-the-middle attackers to disable bidirectional authentication and obtain sensitive information by forcing a downgrade to simple authentication. (CVSS:3.2) (Last Update:2014-04-24)