type command - env x=\'() { :;}; echo vulnerable\' bash -c \'echo hello\'
in your terminal.
if your system is vulnerable then above command will return output like above
vulnerable hello
all the Debian /Ubuntu user to patch it kindly update your bash to latest version
run bash --version command to know your currently installed version
run- sudo apt-get update && sudo apt-get install –only-upgrade bash
run- sudo apt-get update && sudo apt-get install –only-upgrade bash
if your system is alread updated then just simply upgrade your bash version by running this command
sudo apt-get install --only-upgrade bash
http://vtechcoder.blogspot.in/2014/09/how-to-find-and-fix-bash-shell-shock.html