I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments. Concise Binary Object Representation, CBOR (RFC7049) is a binary data format of JSON optimized for IoT. This document describes the JSON and CBOR formats of the CoRE link format of RFC-6690. The document's security section refers to the security sections of the respective formats' RFCs, [RFC6690], [RFC7049] and [RFC7159]. These describe the various issues well. This document introduces no new issues that require further security considerations.