CVE-2026-42211: React router Remote Code Execution Vulnerability

HIGH
Advisory Identifier: GHSA-49rj-9fvp-4h2h
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CVSS 8.1
CWE-502
Published
Advisory Summary

CVE-2026-42211 is a HIGH (CVSS 8.1) remote code execution vulnerability (CWE-502: Deserialization of Untrusted Data) affecting React router libraries in the npm ecosystem. The issue involves react router's vendored turbo-stream v2 allows arbitrary constructor invocation via type_error deserialization leading to unauth rce. Remediation is available by upgrading affected packages to version 7.14.2.

CVE-2026-42211 at a Glance

CVE Identifier CVE-2026-42211
GHSA Identifier GHSA-49rj-9fvp-4h2h
Severity HIGH
CVSS v3.1 Base Score 8.1
CWE Classification CWE-502: Deserialization of Untrusted Data
Affected Product React router
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 8.1

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:N/S:U/C:H/I:H/A:H).

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

How to Fix CVE-2026-42211

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: 7.14.2 
npm install react-router@7.14.2
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-2026-42211, 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 7.14.2), 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-502: Deserialization of Untrusted Data, where the product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid. 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

When using React Router v7 in [Framework Mode](https://reactrouter.com/start/modes#framework), there exists a combination of steps that could potentially allow unauthorized RCE through external requests. This first requires the application code to have an existing prototype pollution vulnerability. This can be leveraged into a 2-step attack in which the second step can trigger unauthorized RCE on the remote server. > [!NOTE] > This does not impact your React Router application if you are using [Declarative Mode](https://reactrouter.com/start/modes#declarative) (`<BrowserRouter>`) or [Data Mode](https://reactrouter.com/start/modes#data) (`createBrowserRouter`/`<RouterProvider>`).

CVE-2026-42211 Affected React router Versions

1 component(s)
Fixed Versions:
7.14.2
Product / Package Ecosystem Affected Versions Fixed Version
react-router
npm/react-router
npm
≥ 7.0.0
< 7.14.2
7.14.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/remix-run/react-router/security/advisories/GHSA-49rj-9fvp-4h2h
NVD — CVE-2026-42211 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-42211
React router Source Repository REPOSITORY
https://github.com/remix-run/react-router

Frequently Asked Questions

What is CVE-2026-42211?
CVE-2026-42211 is a security vulnerability in React router involving React Router's vendored turbo-stream v2 allows arbitrary constructor invocation via TYPE_ERROR deserialization leading to Unauth RCE under CWE-502: Deserialization of Untrusted Data.
Which React router versions are affected?
Affected versions include releases prior to 7.14.2 across affected packages: react-router.
What version fixes CVE-2026-42211?
Upgrading to 7.14.2 (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 7.14.2. Upgrade your dependency to 7.14.2 or later.
What is the CVSS score of CVE-2026-42211?
CVE-2026-42211 has a CVSS v3.1 base score of 8.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-42211?
CVE-2026-42211 is classified under CWE-502: Deserialization of Untrusted Data (The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.).
How can I check npm dependencies for CVE-2026-42211?
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-49rj-9fvp-4h2h",
  "modified" : "2026-06-03T21:03:32Z",
  "published" : "2026-06-03T21:03:32Z",
  "aliases" : [ "CVE-2026-42211" ],
  "summary" : "React Router's vendored turbo-stream v2 allows arbitrary constructor invocation via TYPE_ERROR deserialization leading to Unauth RCE",
  "details" : "When using React Router v7 in [Framework Mode](https://reactrouter.com/start/modes#framework), there exists a combination of steps that could potentially allow unauthorized RCE through external requests.  This first requires the application code to have an existing prototype pollution vulnerability.  This can be leveraged into a 2-step attack in which the second step can trigger unauthorized RCE on the remote server.\n\n> [!NOTE]\n> This does not impact your React Router application if you are using [Declarative Mode](https://reactrouter.com/start/modes#declarative) (`<BrowserRouter>`) or [Data Mode](https://reactrouter.com/start/modes#data) (`createBrowserRouter`/`<RouterProvider>`).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "react-router"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.0.0"
      }, {
        "fixed" : "7.14.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 7.14.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/remix-run/react-router/security/advisories/GHSA-49rj-9fvp-4h2h"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-42211"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/remix-run/react-router"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-03T21:03:32Z",
    "nvd_published_at" : "2026-06-02T20:16:36Z"
  }
}