Shellshock vulnerability
On 24th Sept 2014, a bash vulnerability, now known as ShellShock was disclosed. The vulnerability allowed attackers to execute arbitrary code by passing strings against environment variables.
This is affecting all unix based systems with bash version between 1.14 and 4.3.
Checking System Vulnerability
env VAR='() { :;}; echo Bash is unsafe!' bash -c "echo Test Complete"
Fix
An incomplete fix is currently available but a complete fix is in the pipeline as we speak.
Whether its a complete fix or not update your bash now!
# debian
sudo apt-get update && sudo apt-get install --only-upgrade bash