This indicates an attack attempt to exploit a Remote Command Execution vulnerability in Apache Hadoop.
The vulnerability is due to insufficient validation on user input when the vulnerable software handles a maliciously crafted HTTP request. A remote attacker may be able to exploit this to execute arbitrary command or code within the context of the application, via a crafted HTTP request.
Apache Hadoop 2.8.1 and prior
System Compromise: Remote attackers can gain control of vulnerable systems.
Currently we are unaware of any vendor provided patch for this issue.