PT-2026-33034 · Fastify · Fastify-Express

Climba03003 + 3 · Published 2026-04-15 · Updated 2026-04-15 · CVE-2026-33807

Mitre

CVSS v3.1

9.1

Critical

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

@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.

Upgrade to @fastify/express v4.0.5 or later.

Fix

Weakness Enumeration

CWE-436

Related Identifiers

CVE-2026-33807

Affected Products

Fastify-Express

References · 2

• https://cna.openjsf.org/security-advisories.html · Note
• https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c · Note