How to find and fix Bash Shell-shock vulnerability CVE-2014-6271 in unix like system

In the world wide hurly-burly of personal network system and server security risk of these days due to Bash Shell-shock vulnerability CVE-2014-6271, so what should we do i suggest ...

Keep Calm And Patch

so lets begin to check if you system is vulnerability to bash shell-shock vulnerability  

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

if your system is alread updated then just simply upgrade your bash version by running this command 

sudo apt-get install --only-upgrade bash

again check your bash version after upgrading your bash version my previous version was version 3.2

----------------------------------------------------------------

update the bash using yum on all RedHat/CentOS 

run- yum update bash

On RedHat 6 (and CentOS 6), I had the following bash version before the fix:

run- # rpm -qa | grep bash

bash-3.2-33.el5_11.4

now again check your system if vulnerable or not by using this command 

run- cd /tmp; rm -f /tmp/echo; env 'x=() { (a)=>\' bash -c "echo date"; cat /tmp/echo

if you are not vulnerable then out put will be like

no content will be displayed and if it is still vulnerable then it will show content of file like 

bash: x: line 1: syntax error near unexpected token `=' 

bash: x: line 1: `' bash: error importing function definition for `x' 

Fri Sep 26 16:15:09 PDT 2014

------------------------------------------------------------------------------------------------------------------------------

if you have more than one server to update use this script to do all at once

#!/bin/bash

# This script will log into each of your servers and execute the command below

servers=(

# Put your list of servers here

111.222.333.444

123.123.123.123

10.10.10.10

15.22.22.22

)

for server in ${servers[@]}

do

# Here's the command you're going to run on each

ssh $server 'yum -y update bash'

done