Authentication/Authorization Bypass in @fastify/middie Path-Scoped Middleware
CVE-2026-2880 is an improper path normalization vulnerability in the Node.js package @fastify/middie affecting versions prior to 9.2.0. The issue occurs when applications use path-scoped middleware, such as app.use('/secret', auth), and Fastify router normalization options are enabled. Under combinations of normalization behaviors including ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash handling, crafted request paths can be interpreted differently by middleware matching versus route resolution. As a result, middleware-based authentication or authorization checks may be skipped while the request is still routed to the intended protected handler.
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An improper path normalization vulnerability in @fastify/middie that can contribute to middleware bypass conditions.
Authentication/authorization bypass in @fastify/middie (< 9.2.0) involving path-scoped middleware and Fastify router path-normalization options, allowing crafted paths to bypass middleware checks while still reaching protected routes/handlers.
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