# Remix and React Router allow URL manipulation via Host / X-Forwarded-Host headers

Advisory record · `GHSA-4q56-crqp-v477`

- **Identifiers:** `GHSA-4q56-crqp-v477` · `CVE-2025-31137`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-444](https://cwe.mitre.org/data/definitions/444.html)
- **Tags:** [HTTP request smuggling](https://agentprime.io/advisories/tag/request-smuggling.md)
- **Published:** 1 Apr 2025
- **Updated:** 1 Apr 2025
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 1 Apr 2025, 22:23 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `@react-router/express` (npm): affected `>=7.0.0, <7.4.1`; fixed in `7.4.1`
- `@remix-run/express` (npm): affected `>=2.11.1, <2.16.3`; fixed in `2.16.3`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.5 High, CVSS 3.0: `CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.012, the 68th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 1 Apr 2025. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-4q56-crqp-v477](https://github.com/advisories/GHSA-4q56-crqp-v477)
- [OSV: GHSA-4q56-crqp-v477](https://osv.dev/vulnerability/GHSA-4q56-crqp-v477)
- <https://github.com/remix-run/react-router/security/advisories/GHSA-4q56-crqp-v477>
- <https://nvd.nist.gov/vuln/detail/CVE-2025-31137>
- <https://github.com/remix-run/react-router>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-4q56-crqp-v477>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-4q56-crqp-v477/>. Everything for agents: <https://agentprime.io/llms.txt>.