Nest is a framework for building scalable Node.js server-side applications. Versions prior to 11.1.11 have a Fastify URL encoding middleware bypass. A NestJS application is vulnerable if it uses `@nestjs/platform-fastify`; relies on `NestMiddleware` (via `MiddlewareConsumer`) for security checks (authentication, authorization, etc.), or through `app.use()`; and applies middleware to specific routes using string paths or controllers (e.g., `.forRoutes('admin')`). Exploitation can result in unauthenticated users accessing protected routes, restricted administrative endpoints becoming accessible to lower-privileged users, and/or middleware performing sanitization or validation being skipped. This issue is patched in `@nestjs/platform-fastify@11.1.11`.

Nest has a Fastify URL Encoding Middleware Bypass (TOCTOU)