$ env x=’() { :;}; echo vulnerable’ bash -c “echo this is a test” vulnerable this is a test
yum -y update bash
$ env x=’() { :;}; echo vulnerable’ bash -c “echo this is a test” bash: warning: x: ignoring function definition attempt bash: error importing function definition for `x’ this is a test
https://securityblog.redhat.com/2014/09/24/bash-specially-crafted-environment-variables-code-injection-attack/