CVE-2026-25223 PUBLISHED

Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.2, a validation bypass vulnerability exists in Fastify where request body validation schemas specified by Content-Type can be completely circumvented. By appending a tab character (\t) followed by arbitrary content to the Content-Type header, attackers can bypass body validation while the server still processes the body as the original content type. This issue has been patched in version 5.7.2.

• https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmq
• https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821
• https://hackerone.com/reports/3464114
• https://fastify.dev/docs/latest/Reference/Validation-and-Serialization
• https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125
• https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272

• CWE-436: Interpretation Conflict CWE