Improper Access Control

@fastify/express is vulnerable to Improper Access Control. The vulnerability is due to incorrect path handling in the onRegister function, where middleware paths are duplicated when inherited by child plugins, causing them to not match incoming requests and resulting in bypass of security control...

EUVD-2026-22880

@fastify/express's middleware path doubling causes authentication bypass in child plugin scopes...

CVE-2026-33807

@fastify/express v4.0.4 and earlier contains a path handling bug in the onRegister function that causes middleware paths to be doubled when inherited by child plugins. When a child plugin is registered with a prefix that matches a middleware path, the middleware path is prefixed a second time,...

CVE-2026-33807 @fastify/express vulnerable to middleware path doubling causing authentication bypass in child plugin scopes

@fastify/express v4.0.4 and earlier contains a path handling bug in the onRegister function that causes middleware paths to be doubled when inherited by child plugins. When a child plugin is registered with a prefix that matches a middleware path, the middleware path is prefixed a second time,...

PT-2026-33034

Name of the Vulnerable Software and Affected Versions @fastify/express versions prior to 4.0.5 Description A path handling bug in the onRegister function causes middleware paths to be doubled when inherited by child plugins. When a child plugin is registered with a prefix matching a middleware...