CVE-2025-31137: Remix and React Router allow URL manipulation via Host / X-Forwarded-Host headers
Description
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.
Classification
CVE ID: CVE-2025-31137
CVSS Base Severity: HIGH
CVSS Base Score: 7.5
CVSS Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Problem Types
CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')Affected Products
Vendor: remix-run
Product: react-router
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.06% (probability of being exploited)
EPSS Percentile: 17.87% (scored less or equal to compared to others)
EPSS Date: 2025-04-30 (when was this score calculated)
References
https://nvd.nist.gov/vuln/detail/CVE-2025-31137https://github.com/remix-run/react-router/security/advisories/GHSA-4q56-crqp-v477