Just type this command in your SSH shell

$ env x='() { :;}; echo vulnerable' bash -c 'echo hello'

If you got this output then you are safe:
bash: warning: x: ignoring function definition attempt
bash: error importing function definition for `x'
hello

If you got this output then you are vulnerable and need to update:
vulnerable

Here is the tutorial how to do it:
https://brew.sh/

• bash bug
• exploit
• hacking
• linux security flaws
• system administration
• threat
• vulnerability