Vulnerabilities in pkg:npm/@remix-run/express

PACKAGE
Advisory Identifier: GHSA-4q56-crqp-v477
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Advisory Summary

CVE-2025-31137 is a HIGH (CVSS 7.5) remix and react router allow vulnerability (CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')) affecting @react router/express libraries in the npm ecosystem. The issue involves remix and react router allow url manipulation via host / x-forwarded-host headers. Remediation is available by upgrading affected packages to version 7.4.1, 2.16.3.

1 Known Advisory Record(s)
Package Vulnerability Intelligence

pkg:npm/@remix-run/express

1 Known Advisory Record(s)

Vulnerability advisories affecting package pkg:npm/@remix-run/express. Select an advisory below to view technical details or fixes.

Advisory ID CVE / NVD Severity Summary
GHSA-4q56-crqp-v477 CVE-2025-31137 HIGH Remix and React Router allow URL manipulation via Host / X-Forwarded-Host headers

CVE-2025-31137 at a Glance

CVE Identifier CVE-2025-31137
GHSA Identifier GHSA-4q56-crqp-v477
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Affected Product @react router/express
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2025-31137

To remediate this vulnerability, upgrade all affected @react router/express dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@react-router/express fixed: 7.4.1 
npm install @react-router/express@7.4.1
@remix-run/express fixed: 2.16.3 
npm install @remix-run/express@2.16.3
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @react-router/express

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2025-31137, inspect your project dependencies using npm:

npm ls @react-router/express

Analyze the terminal output to locate any version of @react router/express in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 7.4.1), your application is affected.

Note: The npm ls @react-router/express command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'), where the product acts as an intermediary http agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed http requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. In @react router/express, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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_)

CVE-2025-31137 Affected @react router/express Versions

2 component(s)
Fixed Versions:
7.4.12.16.3
Product / Package Ecosystem Affected Versions Fixed Version
@react-router/express
npm/@react-router/express
npm
≥ 7.0.0
< 7.4.1
7.4.1
@remix-run/express
npm/@remix-run/express
npm
≥ 2.11.1
< 2.16.3
2.16.3

References

GitHub Advisory / Wiki ADVISORY
https://github.com/remix-run/react-router/security/advisories/GHSA-4q56-crqp-v477
NVD — CVE-2025-31137 NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-31137
@react router/express Source Repository REPOSITORY
https://github.com/remix-run/react-router

Frequently Asked Questions

What is CVE-2025-31137?
CVE-2025-31137 is a security vulnerability in @react router/express involving Remix and React Router allow URL manipulation via Host / X-Forwarded-Host headers under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling').
Which @react router/express versions are affected?
Affected versions include releases prior to 7.4.1, 2.16.3 across affected packages: @react-router/express, @remix-run/express.
What version fixes CVE-2025-31137?
Upgrading to 7.4.1, 2.16.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @react-router/express affected?
Yes, @react-router/express is affected in releases prior to 7.4.1. Upgrade your dependency to 7.4.1 or later.
Is @remix-run/express affected?
Yes, @remix-run/express is affected in releases prior to 2.16.3. Upgrade your dependency to 2.16.3 or later.
What is the CVSS score of CVE-2025-31137?
CVE-2025-31137 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2025-31137?
CVE-2025-31137 is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') (The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.).
How can I check npm dependencies for CVE-2025-31137?
Run the dependency tree command: 'npm ls @react-router/express'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4q56-crqp-v477",
  "modified" : "2025-04-01T22:23:33Z",
  "published" : "2025-04-01T22:23:33Z",
  "aliases" : [ "CVE-2025-31137" ],
  "summary" : "Remix and React Router allow URL manipulation via Host / X-Forwarded-Host headers",
  "details" : "### Impact\n\nWe 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.\n\n### Patches\n\nThis issue has been patched and released in Remix 2.16.3 React Router 7.4.1.\n\n### Credits\n\n- Rachid Allam (zhero;)\n- Yasser Allam (inzo_)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
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      "name" : "@react-router/express"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.0.0"
      }, {
        "fixed" : "7.4.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@remix-run/express"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.11.1"
      }, {
        "fixed" : "2.16.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/remix-run/react-router/security/advisories/GHSA-4q56-crqp-v477"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-31137"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/remix-run/react-router"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-444" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-04-01T22:23:33Z",
    "nvd_published_at" : "2025-04-01T19:15:45Z"
  }
}