Full title: Dhclient Bash Environment Variable Injection Exploit 
Category: remote exploits
Platform: linux
When bash is started with an environment variable that begins with the string "() {", that variable is treated as a function definition and parsed as code. If extra commands are added after the function definition, they will be executed immediately. When dhclient receives an ACK that contains a domain name or hostname, they are passed to configuration scripts as environment variables, allowing us to trigger the bash bug. Because of the length restrictions and unusual networking scenario at time of exploitation, this Metasploit module achieves code execution by echoing our payload into /etc/crontab and cleans it up when we get a shell.

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