cvedb.io
CVE-2026-33807
CRITICAL · CVSS 9.1
EPSS exploitation probability: 0%
Published 2026-04-15T10:16:48.310 · Last modified 2026-06-17T10:38:07.653

Summary

@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.

Affected products

fastify — fastify\/express

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References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.