CVE-2026-53667: React Router Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-h8fp-f39c-q6mh
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CVSS 6.9
CWE-79
Published
Advisory Summary

CVE-2026-53667 is a MODERATE (CVSS 6.9) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting React Router libraries in the npm ecosystem. The issue involves rscerrorhandler missing protocol validation (xss). Remediation is available by upgrading affected packages to version 7.18.0.

CVE-2026-53667 at a Glance

CVE Identifier CVE-2026-53667
GHSA Identifier GHSA-h8fp-f39c-q6mh
Severity MODERATE
CVSS v3.1 Base Score 6.9
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product React Router
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 6.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N).

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

How to Fix CVE-2026-53667

To remediate this vulnerability, upgrade all affected React Router 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 fixed: 7.18.0 
npm install react-router@7.18.0
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

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-53667, inspect your project dependencies using npm:

npm ls react-router

Analyze the terminal output to locate any version of React Router in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 7.18.0), your application is affected.

Note: The npm ls react-router 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-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In React Router, 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

This is a follow up to https://github.com/remix-run/react-router/security/advisories/GHSA-8646-j5j9-6r62. React Router was alerted of a code path in the (unstable) RSC error handling path in which redirects from untrusted sources could still result in an XSS vector via attacker-supplied redirect targets > [!NOTE] > This only affects your application if you are using the unstable RSC APIs

CVE-2026-53667 Affected React Router Versions

1 component(s)
Fixed Versions:
7.18.0
Product / Package Ecosystem Affected Versions Fixed Version
react-router
npm/react-router
npm
≥ 7.11.0
< 7.18.0
7.18.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/remix-run/react-router/security/advisories/GHSA-h8fp-f39c-q6mh
React Router Source Repository REPOSITORY
https://github.com/remix-run/react-router/pull/15177
Security Fix Commit FIX COMMIT
https://github.com/remix-run/react-router/commit/ce596e823f0d7b883a433af1d5a839a8b9fe0242
React Router Source Repository REPOSITORY
https://github.com/remix-run/react-router
React Router Source Repository REPOSITORY
https://github.com/remix-run/react-router/blob/main/CHANGELOG.md#v7180
React Router Release RELEASE
https://github.com/remix-run/react-router/releases/tag/react-router@7.18.0

Frequently Asked Questions

What is CVE-2026-53667?
CVE-2026-53667 is a security vulnerability in React Router involving RSCErrorHandler Missing Protocol Validation (XSS) under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which React Router versions are affected?
Affected versions include releases prior to 7.18.0 across affected packages: react-router.
What version fixes CVE-2026-53667?
Upgrading to 7.18.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is react-router affected?
Yes, react-router is affected in releases prior to 7.18.0. Upgrade your dependency to 7.18.0 or later.
What is the CVSS score of CVE-2026-53667?
CVE-2026-53667 has a CVSS v3.1 base score of 6.9 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N.
What CWE is associated with CVE-2026-53667?
CVE-2026-53667 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check npm dependencies for CVE-2026-53667?
Run the dependency tree command: 'npm ls react-router'. 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-h8fp-f39c-q6mh",
  "modified" : "2026-07-23T19:35:57Z",
  "published" : "2026-07-23T19:35:57Z",
  "aliases" : [ "CVE-2026-53667" ],
  "summary" : "React Router: RSCErrorHandler Missing Protocol Validation (XSS)",
  "details" : "This is a follow up to https://github.com/remix-run/react-router/security/advisories/GHSA-8646-j5j9-6r62.  React Router was alerted of a code path in the (unstable) RSC error handling path in which redirects from untrusted sources could still result in an XSS vector via attacker-supplied redirect targets\n\n> [!NOTE]\n> This only affects your application if you are using the unstable RSC APIs",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "react-router"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.11.0"
      }, {
        "fixed" : "7.18.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/remix-run/react-router/security/advisories/GHSA-h8fp-f39c-q6mh"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/remix-run/react-router/pull/15177"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/remix-run/react-router/commit/ce596e823f0d7b883a433af1d5a839a8b9fe0242"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/remix-run/react-router"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/remix-run/react-router/blob/main/CHANGELOG.md#v7180"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/remix-run/react-router/releases/tag/react-router@7.18.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-23T19:35:57Z",
    "nvd_published_at" : null
  }
}