CVE-2025-31137: Remix-Run React-Router

High severity, CVSS 7.5. EPSS: 1.2% chance of exploitation in the next 30 days.

React Router is a multi-strategy router for React bridging the gap from React 18 to React 19. There is a vulnerability in Remix/React Router that affects all Remix 2 and React Router 7 consumers using the Express adapter. Basically, this vulnerability allows anyone to spoof the URL used in an incoming Request by putting a URL pathname in the port section of a URL that is part of a Host or X-Forwarded-Host header sent to a Remix/React Router request handler. This issue has been patched and released in Remix 2.16.3 and React Router 7.4.1.

Affected products

• Remix-Run React-Router: from 7.0.0, before 7.4.1 (fixed in 7.4.1); from 2.11.1, before 2.16.3 (fixed in 2.16.3)

Published 2025-04-01. Last modified 2026-06-17.