CVE-2026-33807
CVE-2026-33807 · @fastify/express vulnerable to middleware path doubling causing authentication bypass in child plugin scopes
This page contains facts from public vulnerability sources. Check the original advisory before updating.
@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.
CVSS 9.1 · Critical · EPSS 0.4% · Fix available
- Published
- Updated
Stack: node
Affected products and versions
@fastify/express
- Versions
- ≥ 0, < 4.0.5: Affected (semver)
- 4.0.5: Not affected (semver)
Update to 4.0.5
@fastify/express npm
- Affected ranges
- SEMVER: < 4.0.5
Update to 4.0.5