This is an information disclosure vulnerability in Apache Hadoop before 2.6.4 and 2.7.x before 2.7.2 in the short-circuit reads feature of HDFS. A local user on an HDFS DataNode may be able to craft a block token that grants unauthorized read access to random files by guessing certain fields in the token.

Apache Hadoop 2.6.x encrypts intermediate data generated by a MapReduce job and stores it along with the encryption key in a credentials file on disk when the Intermediate data encryption feature is enabled, which allows local users to obtain sensitive information by reading the file.