Command-line access means a user can run a program directly on a host through a shell or similar local interface, instead of reaching it over the network. In security terms, this is important because the attacker already has a foothold on the system, even if only as an unprivileged local user.
Local access matters in exploit paths that depend on filesystem behavior, privilege boundaries, or trusted admin tools. For example, a flaw in a server’s spool handling may be reachable only when someone can invoke the program locally and provide crafted arguments or trigger its internal file operations. Defenders treat command-line entry points as part of the attack surface: restrict who can log in, audit scripts and wrappers that call privileged programs, and patch software that mishandles local input or paths. A vulnerability that requires command-line access is not harmless; on multi-user systems, it can still lead to file disclosure or privilege escalation.