CVE-2026-2880 HIGH

CVE-2026-2880: @fastify/middie has an improper path normalization vulnerability

Vendor @Fastify/Middie
Product @fastify/middie
Weakness CWE-20 · Input validation
Published February 27, 2026
Last update February 27, 2026

CVSS base score

8.2/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

February 27, 2026 CVE published
February 27, 2026 Record updated