A minimal runtime is a stripped-down execution environment that keeps only the essential components needed to run code. It may include a small parser, basic control flow, and a limited standard library, while omitting convenience features, extensive error handling, or broad system access.
In cyber security, minimal runtimes matter because they change the attack surface. Fewer features can mean fewer bugs, less complexity to audit, and tighter control over what code is allowed to do. Defenders use minimal runtimes in sandboxes, embedded systems, and specialized interpreters to reduce risk. Attackers may also exploit them by assuming missing checks, weak validation, or unsupported behavior that causes unexpected parsing or execution results. The key security question is not just whether the runtime is small, but what it explicitly accepts, rejects, and isolates.