What is a Shellshock vulnerability?

Shellshock allows attackers to inject and execute arbitrary commands in a system's Bash shell by appending malicious code to specially crafted environment variables, which is the definition of command injection.

Cross-site scripting (XSS) is a client-side code injection vulnerability typically affecting web applications, not a shell vulnerability.

A heap overflow involves writing more data than allocated to a memory buffer in the heap, leading to memory corruption, which is a different class of vulnerability.

SQL injection targets databases by inserting malicious SQL code into input fields, which is distinct from a shell command execution flaw.