CVE-2026-44575

Next.js is a React framework for building full-stack web applications. From 15.2.0 to before 15.5.16 and 16.2.5, App Router applications that rely on middleware or proxy-based checks for authorization can allow unauthorized access through transport-specific route variants used for segment prefetching. In affected configurations, specially crafted .rsc and segment-prefetch URLs can resolve to the same page without being matched by the intended middleware rule, which can allow protected content to be reached without the expected authorization check. This vulnerability is fixed in 15.5.16 and 16.2.5.

### Impact App Router applications that rely on middleware or proxy-based checks for authorization can allow unauthorized access through transport-specific route variants used for segment prefetching. In affected configurations, specially crafted `.rsc` and segment-prefetch URLs can resolve to the same page without being matched by the intended middleware rule, which can allow protected content to be reached without the expected authorization check. ### Fix We now include App Router transport variants when generating middleware matchers, so middleware protections are applied consistently to those requests as well as to the normal page URL. ### Workarounds If you cannot upgrade immediately, enforce authorization in the underlying route or page logic instead of relying solely on middleware.

### Impact App Router applications that rely on middleware or proxy-based checks for authorization can allow unauthorized access through transport-specific route variants used for segment prefetching. In affected configurations, specially crafted `.rsc` and segment-prefetch URLs can resolve to the same page without being matched by the intended middleware rule, which can allow protected content to be reached without the expected authorization check. ### Fix We now include App Router transport variants when generating middleware matchers, so middleware protections are applied consistently to those requests as well as to the normal page URL. ### Workarounds If you cannot upgrade immediately, enforce authorization in the underlying route or page logic instead of relying solely on middleware.

Next.js es un framework de React para construir aplicaciones web full-stack. Desde 15.2.0 hasta antes de 15.5.16 y 16.2.5, las aplicaciones de App Router que dependen de middleware o de comprobaciones basadas en proxy para la autorización pueden permitir acceso no autorizado a través de variantes de ruta específicas del transporte utilizadas para la precarga de segmentos. En configuraciones afectadas, las URL .rsc y de precarga de segmentos especialmente diseñadas pueden resolverse a la misma página sin ser igualadas por la regla de middleware prevista, lo que puede permitir que se acceda a contenido protegido sin la comprobación de autorización esperada. Esta vulnerabilidad está corregida en 15.5.16 y 16.2.5.