03.16.03 External System Services
What the standard requires
a. Require the providers of external system services used for the processing, storage, or transmission of CUI to comply with the following security requirements: [security requirements]. b. Define and document user roles and responsibilities with regard to external system services, including shared responsibilities with external service providers. c. Implement processes, methods, and techniques to monitor security requirement compliance by external service providers on an ongoing basis.
Quoted verbatim from NIST SP 800-171 Rev 3, which is in the public domain.
Cross-framework mappings
No cross-framework mapping is seeded for this control. That is stated rather than filled in: a mapping nobody authored is worse than a gap you can see.
In CMDash this control is a row with an owner, a status, uploaded evidence kept with its full history, and an export an assessor can read.