In software development, a NULL pointer is a pointer variable that does not reference any valid memory location. Dereferencing such a pointer—attempting to access the memory it supposedly points to—results in undefined behaviour. In many systems, this leads to crashes, data corruption, or even exploitable vulnerabilities.
OS Command Injection occurs when an application dynamically constructs operating system (OS) commands using untrusted inputs, enabling an attacker to execute arbitrary commands on the host system. These commands often run with the same privileges as the application, amplifying the potential impact.
A PHP web shell is a script, written in PHP, that allows attackers to execute commands on a compromised web server remotely. These scripts act as a backdoor, providing attackers with access to sensitive data, server resources, and the capability to escalate their attack.