Can someone explain the Shell Shock Bash code?

env x='() { :;}; echo vulnerable' bash -c "echo this is a test"

what env

does it do?
Documents env

run programs in a modified environment

env [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]

it is clear that x

is the name / variable and () { :;}; echo vulnerable'

is the value of the variable

now what is it () { :;};

?
when the function is exported bash stores its defenition as the value of an environment variable

$ x() {echo hello world;}
$ export x
$ env | grep x
x=() {echo hello world};

      

        
        
        
      

    

now when x='() {:;}'

means similar spelling

$ x() {:;}
$ export x
$ env | grep x

      

        
        
        
      

    

We did this indirectly export x

on a new environment created env


here :

- this is the null statement in bash

Hope it helps