Attack Surface
The set of reachable interfaces, components, privileges, data paths, and behaviors through which a system may be attacked.
Security Context
The attack surface is the set of reachable interfaces, privileges, components, data paths, and behaviors through which an adversary can interact with a system. Unnecessary endpoints, open ports, excessive privileges, and a complex dependency graph all expand that surface, so inventory and exposure changes must be tracked over time.
Threat-Model Boundary
An attack surface is not the same thing as a single vulnerability. It describes the space in which attacks may be attempted; a vulnerability is a specific weakness within that space.