In certain IETF OAuth 2.0-related specifications, when the JSON Web Token Profile for OAuth 2.0 Client Authentication mechanism is used, there are ambiguities in the audience values of JWTs sent to authorization servers. The affected RFCs may include RFC 7523, and also RFC 7521, RFC 7522, RFC 9101 (JAR), and RFC 9126 (PAR).
The authentication algorithm is sound, but the implemented mechanism can be bypassed as the result of a separate weakness that is primary to the authentication error.