CVE-2026-33807

9.1 CRITICAL
Published: April 15, 2026 Modified: June 01, 2026
View on NVD

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

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://cna.openjsf.org/security-advisories.html
Source: ce714d77-add3-4f53-aff5-83d477b104bb
Vendor Advisory
https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c
Source: ce714d77-add3-4f53-aff5-83d477b104bb
Exploit Mitigation Vendor Advisory
https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Exploit Mitigation Vendor Advisory

3 reference(s) from NVD

Quick Stats

CVSS v3 Score
9.1 / 10.0
EPSS (Exploit Probability)
0.0%
12th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

fastify