CVE-2026-6556

@fastify/express versions 4.0.6 and earlier only rewrite the plugin prefix for middleware mount paths when the path argument is a string. Non-string mount paths arrays of paths and regular expressions are left unprefixed inside prefixed plugin scopes, so middleware registered with those forms doe...

CVE-2026-6556 @fastify/express vulnerable to middleware bypass via non-string mount paths in prefixed plugins

@fastify/express versions 4.0.6 and earlier only rewrite the plugin prefix for middleware mount paths when the path argument is a string. Non-string mount paths arrays of paths and regular expressions are left unprefixed inside prefixed plugin scopes, so middleware registered with those forms doe...

CVE-2026-6556

The CVE concerns @fastify/express 4.0.6 and earlier, where non-string mount paths (arrays/regex) are not prefixed inside prefixed plugin scopes. This causes middleware registered with those forms to not match the actual prefixed request path, potentially bypassing path-scoped security middleware ...

PT-2026-53878

Name of the Vulnerable Software and Affected Versions @fastify/express versions prior to 4.0.7 Description A middleware scoping flaw exists where plugin prefixes are not applied to middleware mount paths when the mount path is provided as an array or a regular expression. This occurs due to...

CVE-2026-33808

Impact@fastify/express v4.0.4 and earlier fails to normalize URLs before passing them to Express middleware when Fastify router normalization options are enabled. This allows complete bypass of path-scoped authentication middleware via duplicate slashes when ignoreDuplicateSlashes is enabled, or...

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-2026-22881

@fastify/express has a middleware authentication bypass via URL normalization gaps duplicate slashes and semicolons...

@fastify/express has a middleware authentication bypass via URL normalization gaps (duplicate slashes and semicolons)

Summary @fastify/express v4.0.4 fails to normalize URLs before passing them to Express middleware when Fastify router normalization options are enabled. This allows complete bypass of path-scoped authentication middleware via two vectors: 1. Duplicate slashes //admin/dashboard when...

GHSA-6HW5-45GM-FJ88 @fastify/express has a middleware authentication bypass via URL normalization gaps (duplicate slashes and semicolons)

Summary @fastify/express v4.0.4 fails to normalize URLs before passing them to Express middleware when Fastify router normalization options are enabled. This allows complete bypass of path-scoped authentication middleware via two vectors: 1. Duplicate slashes //admin/dashboard when...

EUVD-2026-22880

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

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

Summary @fastify/express v4.0.4 contains a path handling bug in the onRegister function that causes middleware paths to be doubled when inherited by child plugins. This results in complete bypass of Express middleware security controls for all routes defined within child plugin scopes that share ...

GHSA-HRWM-HGMJ-7P9C @fastify/express's middleware path doubling causes authentication bypass in child plugin scopes

Summary @fastify/express v4.0.4 contains a path handling bug in the onRegister function that causes middleware paths to be doubled when inherited by child plugins. This results in complete bypass of Express middleware security controls for all routes defined within child plugin scopes that share ...

Interpretation Conflict

Overview @fastify/express is an Express compatibility layer for Fastify Affected versions of this package are vulnerable to Interpretation Conflict due to improper handling of middleware paths in the onRegister function. An attacker can gain unauthorized access to protected routes by exploiting t...

Interpretation Conflict

Overview @fastify/express is an Express compatibility layer for Fastify Affected versions of this package are vulnerable to Interpretation Conflict via improper URL normalization gaps. An attacker can gain unauthorized access to protected routes by manipulating the URL path with duplicate slashes...

CVE-2026-33808

Impact@fastify/express v4.0.4 and earlier fails to normalize URLs before passing them to Express middleware when Fastify router normalization options are enabled. This allows complete bypass of path-scoped authentication middleware via duplicate slashes when ignoreDuplicateSlashes is enabled, or...

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,...

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,...

CVE-2026-33807

CVE-2026-33807 affects @fastify/express v4.0.4 and earlier. A path handling bug in onRegister doubles middleware paths when inherited by child plugins, causing the middleware to never match requests. This results in complete bypass of Express middleware security controls (authentication, authoriz...

CVE-2026-33808 @fastify/express vulnerable to middleware authentication bypass via URL normalization gaps (duplicate slashes and semicolons)

Impact@fastify/express v4.0.4 and earlier fails to normalize URLs before passing them to Express middleware when Fastify router normalization options are enabled. This allows complete bypass of path-scoped authentication middleware via duplicate slashes when ignoreDuplicateSlashes is enabled, or...