CVE-2026-3419 Fastify's Missing End Anchor in "subtypeNameReg" Allows Malformed Content-Types to Pass Validation

Fastify incorrectly accepts malformed Content-Type headers containing trailing characters after the subtype token, in violation of RFC 9110 §8.3.1https://httpwg.org/specs/rfc9110.htmlfield.content-type. For example, a request sent with Content-Type: application/json garbage passes validation and ...