CVE-2026-18504

A flaw was found in fastify. A remote attacker can bypass schema validation when a request body schema targets a root primitive value. This occurs because the validation process may coerce a JSON string into an expected type, but the original unvalidated string is then passed to the application...

CVE-2026-18504

fastify is a fast and low overhead web framework for Node.js. Versions of fastify before 5.12.1 are affected by a schema validation bypass when a request body schema targets a root primitive value. When the schema validates a top-level primitive such as an integer, Ajv can coerce a JSON string in...

CVE-2026-18504

fastify versions before 5.12.1 suffer a schema validation bypass: when a route schema targets a root primitive (e.g., integer), Ajv coerces the input type but Fastify passes the original uncoerced value to handlers, letting invalid data reach application logic. Upgrade to 5.12.1; no workarounds e...

CVE-2026-18504 fastify vulnerable to schema validation bypass via root primitive coercion mismatch

fastify is a fast and low overhead web framework for Node.js. Versions of fastify before 5.12.1 are affected by a schema validation bypass when a request body schema targets a root primitive value. When the schema validates a top-level primitive such as an integer, Ajv can coerce a JSON string in...