Improper input validation in Fastify Fastify\/middie
CVE-2026-2880
A vulnerability in @fastify/middie versions < 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)). When Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
EPSS: 0.004 (31.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
Affected products
- Fastify Fastify\/middie
- @Fastify/middie — versions 0.0.0
Weakness classification (CWE)
References
- ce714d77-add3-4f53-aff5-83d477b104bb (Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-2880?
- CVE-2026-2880 is a critical-severity vulnerability in Fastify Fastify\/middie, classified under Improper Input Validation. CVSS score: 9.1/10. Published 2026-02-27.
- How severe is CVE-2026-2880?
- Critical severity. CVSS v3 base score is 9.1 out of 10.