CVE-2026-42342

A flaw was found in React Router and @remix-run/server-runtime. A remote attacker can exploit this vulnerability by sending certain crafted requests to the __manifest endpoint. This can lead to unbounded path expansion, consuming disproportionate server resources. The primary consequence is a denial of service (DoS), resulting in response time degradation and service unavailability for end users.

A flaw was found in React Router (Framework Mode) and Remix (@remix-run/server-runtime). Crafted requests to the __manifest endpoint can trigger unbounded path expansion, consuming disproportionate server resources and causing denial of service through response time degradation or complete service unavailability. This only affects applications using React Router Framework Mode or Remix server runtime; applications using Declarative Mode (BrowserRouter) or Data Mode (createBrowserRouter/RouterProvider) are not impacted. In Red Hat products, affected React Router components are used in internal console UIs that are deployed behind authenticated ingress, reducing the attack surface.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Upgrade to a patched version to fully mitigate the issues (ref: https://github.com/remix-run/react-router/security/advisories/GHSA-8x6r-g9mw-2r78).