CVE-2026-42342: React Router vulnerable to DoS via unbounded path expansion in __manifest endpoint

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-02 · updated 2026-07-21
Weakness: CWE-400

Description

React Router is a router for React. In versions 7.0.0 through 7.14.x of react-router and versions 2.10.0 through 2.17.4 of @remix-run/server-runtime, certain crafted requests can consume disproportionate server resources via unbounded path expansion in the __manifest endpoint, resulting in response time degradation and/or service unavailability for end users. This affects React Router Framework Mode applications as well as Remix applications. This does not impact applications using Declarative Mode (`<BrowserRouter>`) or Data Mode (`createBrowserRouter/<RouterProvider>`). This is patched in react-router version 7.15.0 and @remix-run/server-runtime version 2.17.5.

Affected products

remix-run react-router: from 7.0.0 before 7.15.0 — fixed in 7.15.0
Shopify Remix-Run/Server-Runtime: from 2.10.0 before 2.17.5 — fixed in 2.17.5

How to fix

Upgrade to a fixed version: remix-run react-router 7.15.0; Shopify Remix-Run/Server-Runtime 2.17.5. Check the vendor advisory for mitigations.

References

https://github.com/remix-run/react-router/security/advisories/GHSA-8x6r-g9mw-2r78

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