CVE-2026-84469

A flaw was found in fastify. An unauthenticated remote attacker can bypass request validation by exploiting how fastify processes boolean false schemas. When an application intends to deny all input by assigning 'false' to a route's schema, fastify incorrectly treats it as a missing schema and...

CVE-2026-84469 fastify vulnerable to request validation bypass via skipped boolean false schemas

fastify versions before 5.12.2 decide whether to compile a request schema based on JavaScript truthiness, but JSON Schema Draft 7 defines the boolean false as a valid schema that rejects every instance. When an application assigns false to a route's body, querystring, params, or headers schema to...