How can I update BASH

How can I update BASH? I noticed that there are version 4.2.45 env x='() { :;}; echo vulnerable' bash -c "echo this is a test" this is a test cat /etc/redhat-release CentOS release 5.11 (Final) rpm -q bash bash-3.2-33.el5_11.4 yum update bash Setting up Update Process No Packages marked for Update