Nest has a Fastify URL Encoding Middleware Bypass
What kind of vulnerability is it? Who is impacted? A NestJS application using @nestjs/platform-fastify can allow bypass of any middleware when Fastify path-normalization options (e.g., ignoreTrailingSlash, ignoreDuplicateSlashes, useSemicolonDelimiter) are enabled. In affected route-scoped middleware setups, variant paths may skip middleware checks while still reaching the protected handler. The bug is a path canonicalization mismatch between middleware matching and route matching in Nest’s Fastify adapter. Nest passes Fastify routerOptions (such as …