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. This document appears ready for publication.  This document specifies the CBOR (Compact Binary Object Representation) binary encoding format. The document is generally clearly written, and in particular, is to be commended for providing a clear explanation of why one would want to specify yet another binary encoding for arbitrary objects. One minor note: In the security considerations section, the authors explain potential vulnerabilities in network protocols due to parser errors. (This is good cautionary guidance to provide implementers.) However, at the very end of the section, they suggest that an encoder/decoder used in a security context should provide at least one "strict" mode of operation. I would suggest adding another sentence or two explaining what the phrase "strict mode of operation" means in this context.