CVE-2026-33807
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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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
@fastify/expressnpm | < 4.0.5 | 4.0.5 |
Affected products
3Patches
Vulnerability mechanics
References
4- github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9cnvdExploitMitigationVendor AdvisoryWEB
- cna.openjsf.org/security-advisories.htmlnvdVendor AdvisoryWEB
- github.com/advisories/GHSA-hrwm-hgmj-7p9cghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-33807ghsaADVISORY
News mentions
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