A flaw was found in Next.js, a React framework. A remote attacker can bypass authentication in Next.js applications using App Router built with Turbopack and a single entry in config.i18n.locales by sending crafted requests. This vulnerability allows for unauthorized access, leading to a high impact on confidentiality through information disclosure.

Next.js is a React framework for building full-stack web applications. In versions 16.0.0 through 16.2.10, crafted requests targeting Next.js applications using App Router built with Turbopack and a single entry in config.i18n.locales can bypass middleware/proxy based authentication. This issue has been fixed in version 16.2.11.

Next.js: Middleware / Proxy bypass in App Router applications using Turbopack and single locale