Fastify · @Fastify/Middie · CVE-2026-2880
**Name of the Vulnerable Software and Affected Versions**
@fastify/middie versions prior to 9.2.0
**Description**
A flaw exists in @fastify/middie that can lead to authentication or authorization bypass when path-scoped middleware is used, such as with `app.use('/secret', auth)`. This occurs when Fastify router normalization options are enabled, including options like `ignoreDuplicateSlashes`, `useSemicolonDelimiter`, and trailing-slash behavior. Specifically, specially crafted request paths may circumvent middleware checks while still reaching protected handlers.
**Recommendations**
Update @fastify/middie to version 9.2.0 or later.