CVE-2026-84428

Описание

fastify versions before 5.12.2 implement the case-insensitive nature of HTTP header names by lowercasing names in a route's header schema before compiling it, but the transformation is incomplete: it lowercases the properties keys and the root-level required array, and does not lowercase the trigger and dependent names inside the JSON Schema Draft 7 dependencies keyword. Because Node stores request header names in lowercase, a canonical-case dependency such as requiring an authentication header whenever a privileged-mode header is present never matches, and the presence assertion is silently skipped. An unauthenticated remote client can therefore send the header that activates a privileged branch while omitting the header the dependency was meant to require, bypassing the conditional check. Users should upgrade to fastify 5.12.2 or later.

A flaw was found in fastify. Due to incomplete case normalization of HTTP header names within a route's header schema, specifically within the JSON Schema Draft 7 dependencies keyword, an unauthenticated remote attacker can bypass intended conditional checks. This allows the attacker to send headers that activate privileged functionality without providing the required authentication headers, leading to an authorization bypass.