The attack surface is the sum of all paths for data into and out of the environment, such as network interfaces, applications, services, protocols, ports, and user accounts. The attack surface represents the exposure of the environment to potential threats and attacks. A vulnerability is an exploitable weakness in a system or its design that can allow an attacker to compromise the system or its data. A vulnerability is a subset of the attack surface, as not all paths for data are vulnerable. References: [Understanding Cisco Cybersecurity Operations Fundamentals (CBROPS) - Module 1: Security Concepts]