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.
The Kerberos/MapReduce security functionality in Apache Hadoop 0.20.203.0 through 0.20.205.0, 0.23.x before 0.23.2, and 1.0.x before 1.0.2, as used in Cloudera CDH CDH3u0 through CDH3u2, Cloudera hadoop-0.20-sbin before 0.20.2+923.197, and other products, allows remote authenticated users to impersonate arbitrary cluster user accounts via unspecified vectors.