Shellshock is a vulnerability that has been discovered in Bash, which you are likely to know as the command line interface that you use to manage your Linux server through SSH. On a compromised system, hackers can utilise the Shellshock exploit to run malicious commands that can be used to give them full control of an affected server. These servers can then be grouped together to create botnets that can be used for DDoS attacks amongst other things; the data on affected servers can also be compromised.
Shellshock is a serious bug that lies at the very heart of all Unix-based systems including all Linux distributions and Mac OS X. If you have a Linux-based eNlight virtual machine, Linux VPS, or Linux dedicated server, then you should take immediate action in order to protect your server.
So you’re probably wondering, how do I know if my server’s vulnerable? Well, it’s quite a simple process. First, you need to log in to your Linux server through SSH. In the command line, run the following command:
env x=™() { :;}; echo vulnerable bash c echo this is a test
If this command outputs the following:
vulnerable
this is a test
Then you are using a vulnerable version of Bash. The easiest way to patch the vulnerability is to upgrade to the latest version of Bash, this can be achieved by running yum upgrade bash via SSH. If you re-run our vulnerability test illustrated above once the upgrade is complete, you should receive the following output:
bash: warning: x: ignoring function definition attempt
bash: error importing function definition for x
this is a test
Then you can be sure that your Linux server is patched and will no longer be vulnerable to attack through the Shellshock exploit.
If you want more information on Shellshock or need help with patching your server, please do not hesitate to contact our 24×7 support team.
