The software supply chain is an increasingly common attack vector for malicious actors. The Node.js ecosystem has been subject to a wide array of attacks, likely due to its size and prevalence. To counter such attacks, the research community and practitioners have proposed a range of static and dynamic mechanisms, including process- and language-level sandboxing, permission systems, and taint tracking. Drawing on valuable insight from these works, this paper studies a runtime protection mechanism for (the supply chain of) Node.js applications with the ambitious goals of compatibility, automation, minimal overhead, and policy conciseness. Specifically, we design, implement and evaluate NodeShield, a protection mechanism for Node.js that enforces an application's dependency hierarchy and controls access to system resources at runtime. We leverage the up-and-coming SBOM standard as the source of truth for the dependency hierarchy of the application, thus preventing components from stealthily abusing undeclared components. We propose to enhance the SBOM with a notion of capabilities that represents a set of related system resources a component may access. Our proposed SBOM extension, the Capability Bill of Materials or CBOM, records the required capabilities of each component, providing valuable insight into the potential privileged behavior. NodeShield enforces the SBOM and CBOM at runtime via code outlining (as opposed to inlining) with no modifications to the original code or Node.js runtime, thus preventing unexpected, potentially malicious behavior. Our evaluation shows that NodeShield can prevent over 98% out of 67 known supply chain attacks while incurring minimal overhead on servers at less than 1ms per request. We achieve this while maintaining broad compatibility with vanilla Node.js and a concise policy language that consists of at most 7 entries per dependency.