A flaw was found in React Router. An unauthenticated attacker can send targeted requests to the manifest endpoint, leading to a denial of service (DoS). This can put a heavy load on the server, significantly slowing down response times and impacting the availability of the application.

React Router is a router for React. In versions 7.0.0 through 7.17.0, the manifest endpoint could be accessed via unauthenticated targeted requests that would put heavy load on the server and slow down response times. This issue is a follow up to CVE-2026-42342, and does not does not impact React Router applications using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>). This issue has been fixed in version 7.18.0.

React Router: Unauthenticated Denial of Service via Inefficient Route Matching