PT-2026-53878 · @Fastify/Express · Fastify-Express

Jvr2022 + 1 · Published 2026-06-30 · Updated 2026-06-30 · CVE-2026-6556

Mitre

CVSS v3.1

9.1

Critical

Base vector

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

@fastify/express versions 4.0.6 and earlier only rewrite the plugin prefix for middleware mount paths when the path argument is a string. Non-string mount paths (arrays of paths and regular expressions) are left unprefixed inside prefixed plugin scopes, so middleware registered with those forms does not match the actual prefixed request path. Applications that use path-scoped middleware for authentication, authorization, rate limiting, or auditing on routes inside a prefixed scope can be bypassed by sending a request to the prefixed route, because Fastify still matches the route but the middleware is skipped. Patches: upgrade to @fastify/express 4.0.7. Workarounds: use string mount paths instead of arrays or regular expressions in prefixed plugins, or register one use call per path.

Fix

Improper Authorization

Weakness Enumeration

CWE-285

Related Identifiers

CVE-2026-6556

Affected Products

Fastify-Express

References · 3

• https://nvd.nist.gov/vuln/detail/CVE-2026-6556 · Security Note
• https://github.com/fastify/fastify-express/security/advisories/GHSA-3wf5-7852-vcfq · Note
• https://cna.openjsf.org/security-advisories.html · Note