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OpenAdvisories
High · 8.2 CVE-2026-2880 EUVD-2026-9049GHSA-8p85-9qpw-fwgw

@fastify/middie has an improper path normalization vulnerability

Published Feb 27, 2026 · Updated Feb 27, 2026 · Assigned by openjs

Description

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.

Affected products

VendorProductAffectedFixed
@fastify/middie @fastify/middie 0.0.0 – < 9.2.0 9.2.0

Affected packages

EcosystemPackageAffectedFixedRecord
npm @fastify/middie < 9.2.0 9.2.0 GHSA-8p85-9qpw-fwgw

References