Shellshock vulnerability (Bash Bug) discovered in a large part of Unix systems.


Some time ago, a security flaw was discovered in Unix Operating Systems and derivatives.

This flaw affects the program Bash (Shell), which is used to enter text commands to control the Operating System. This program is included in most Unix legacy Operating Systems, such as Linux, BSD, and Mac OS X.
Users of Android devices are safe because this OS includes another type of Shell called Almquist Shell.

This vulnerability allows attackers to execute commands on the affected machine.

Although this vulnerability affects all systems with Bash installed, users of desktop systems are less likely to be breached due to the very nature of the vulnerability. This is because the attacker must have access to some service connected to the Internet, accepts incoming connections, and uses the Shell Bash in an unsecured manner. Still, running the OS updater and installing the security patches related to this bug is good.

Web servers are one of the most affected systems since programs used to run a web server can use the Bash program, and a skilled attacker could modify the HTTP header sent to the server to exploit the Shellshock vulnerability.

To check if our system is affected by the Shellshock vulnerability, we can enter the system Terminal and type:

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

If our system returns:

this is a test

This means that the system is vulnerable. If it is not vulnerable, it will only show, "this is a test."

If when executing the following command

env X='() { (>>' bash -c "echo date"; cat echo; rm -f echo

the current date is displayed (other lines with errors may be displayed), it means that our system is vulnerable.

What we can do to fix this bug is to install the security updates offered by our Operating System. Most Linux systems already have a security patch for this vulnerability.