CVE-2026-33807
Severity CVSS v4.0:
Pending analysis
Type:
Unavailable / Other
Publication date:
15/04/2026
Last modified:
17/04/2026
Description
@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, causing it to never match incoming requests. This results in complete bypass of Express middleware security controls, including authentication, authorization, and rate limiting, for all routes defined within affected child plugin scopes. No special configuration or request crafting is required.<br />
<br />
Upgrade to @fastify/express v4.0.5 or later.
Impact
Base Score 3.x
9.10
Severity 3.x
CRITICAL