8. Security Considerations

A network-facing application can exhibit vulnerabilities in its processing logic for incoming data. Complex parsers are well known as a likely source of such vulnerabilities, such as the ability to remotely crash a node, or even remotely execute arbitrary code on it. CBOR attempts to narrow the opportunities for introducing such vulnerabilities by reducing parser complexity, by giving the entire range of encodable values a meaning where possible.

Resource exhaustion attacks might attempt to lure a decoder into allocating very big data items (strings, arrays, maps) or exhaust the stack depth by setting up deeply nested items. Decoders need to have appropriate resource management to mitigate these attacks. (Items for which very large sizes are given can also attempt to exploit integer overflow vulnerabilities.)

Applications where a CBOR data item is examined by a gatekeeper function and later used by a different application may exhibit vulnerabilities when multiple interpretations of the data item are possible. For example, an attacker could make use of duplicate keys in maps and precision issues in numbers to make the gatekeeper base its decisions on a different interpretation than the one that will be used by the second application. Protocols that are used in a security context should be defined in such a way that these multiple interpretations are reliably reduced to a single one. To facilitate this, encoder and decoder implementations used in such contexts should provide at least one strict mode of operation (Section 3.10).