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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2025-31137: 1.19% estimated exploitation activity in the next 30 days; percentile 68.01 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact We received a report about 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. Patches This issue has been patched and released in Remix 2.16.3 React Router 7.4.1. Credits - Rachid Allam (zhero;) - Yasser Allam (inzo)

Published by the source

1 Apr 2025, 22:23 UTC

Last modified by the source

1 Apr 2025, 22:42 UTC

Source last checked

26 Oct 2026, 12:36 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-4q56-crqp-v477

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-4q56-crqp-v477

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# Patch Next advisory brief: CVE-2025-31137

Advisory: Remix and React Router allow URL manipulation via Host / X-Forwarded-Host headers
IDs: CVE-2025-31137, GHSA-4q56-crqp-v477
Record: https://patchnext.com/advisories/cve-2025-31137 (revision 2, source checked 26 Oct 2026, 12:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @remix-run/express 2.16.3; @react-router/express 7.4.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @remix-run/express: affected >= 2.11.1, < 2.16.3; fixed in 2.16.3
- npm @react-router/express: affected >= 7.0.0, < 7.4.1; fixed in 7.4.1

## Suggested inspection (read-only)
- `npm ls @remix-run/express --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @react-router/express --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @remix-run/express, @react-router/express.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-4q56-crqp-v477 (OSV record GHSA-4q56-crqp-v477 lists affected ranges: npm @react-router/express >=7.0.0 =2.11.1 <2.16.3 (fixed))
- Verified: https://github.com/advisories/GHSA-4q56-crqp-v477 (GitHub-reviewed advisory GHSA-4q56-crqp-v477 lists affected ranges: npm @react-router/express >=7.0.0 =2.11.1 <2.16.3)

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