Bash vulnerability in linux with Bash

Test with the following (paste into a shell prompt):

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

If you’re vulnerable, you’ll see this:

$ env x='() { :;}; echo vulnerable’ bash -c “echo this is a test”

vulnerable

this is a test

To fix it:

In CentOS:

yum update bash

In Ubuntu:

apt-get install bash

When you run the text code again, you should see this:

$ env x='() { :;}; echo vulnerable’ bash -c “echo this is a test”

bash: warning: x: ignoring function definition attempt

bash: error importing function definition for `x’

this is a test

If you’re using Salt Stack, you could run this to update all your minions’ bash installs:

salt ‘*’ pkg.install bash

There are some more sophisticated ways to do it, especially for larger environments, but I figured I’d mention it.