CVE-2026-55685: React Router Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-chx6-hx7r-mcp5
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CWE-400 CWE-407
Published
Advisory Summary

CVE-2026-55685 is a HIGH denial of service vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting React Router libraries in the npm ecosystem. The issue involves unauthenticated denial of service via inefficient route matching. Remediation is available by upgrading affected packages to version 7.18.0.

CVE-2026-55685 at a Glance

CVE Identifier CVE-2026-55685
GHSA Identifier GHSA-chx6-hx7r-mcp5
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product React Router
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-55685

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-2026-55685, 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-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. 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-8x6r-g9mw-2r78 that covers additional reported scenarios in which the manifest endpoint could be accessed via unauthenticated targeted requests that would put heavy load on the server and slow down response times. > [!NOTE] > This only impacts Framework Mode applications. This does not impact your application if you are using Declarative or Data Mode.

CVE-2026-55685 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
≥ 7.0.0
< 7.18.0
7.18.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/remix-run/react-router/security/advisories/GHSA-chx6-hx7r-mcp5
React Router Source Repository REPOSITORY
https://github.com/remix-run/react-router/pull/15186
Security Fix Commit FIX COMMIT
https://github.com/remix-run/react-router/commit/09e6020d1950e54f361f7ad00938ecd4dde60929
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-2026-55685?
CVE-2026-55685 is a security vulnerability in React Router involving Unauthenticated Denial of Service via Inefficient Route Matching under CWE-400: Uncontrolled Resource Consumption.
Which React Router versions are affected?
Affected versions include releases prior to 7.18.0 across affected packages: react-router.
What version fixes CVE-2026-55685?
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 CWE is associated with CVE-2026-55685?
CVE-2026-55685 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check npm dependencies for CVE-2026-55685?
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-chx6-hx7r-mcp5",
  "modified" : "2026-07-24T14:06:57Z",
  "published" : "2026-07-24T14:06:57Z",
  "aliases" : [ "CVE-2026-55685" ],
  "summary" : "React Router: Unauthenticated Denial of Service via Inefficient Route Matching",
  "details" : "This is a follow up to https://github.com/remix-run/react-router/security/advisories/GHSA-8x6r-g9mw-2r78 that covers additional reported scenarios in which the manifest endpoint could be accessed via unauthenticated targeted requests that would put heavy load on the server and slow down response times.\n\n> [!NOTE]\n> This only impacts Framework Mode applications.  This does not impact your application if you are using Declarative or Data Mode.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "react-router"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.0.0"
      }, {
        "fixed" : "7.18.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/remix-run/react-router/security/advisories/GHSA-chx6-hx7r-mcp5"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/remix-run/react-router/pull/15186"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/remix-run/react-router/commit/09e6020d1950e54f361f7ad00938ecd4dde60929"
  }, {
    "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-400", "CWE-407" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T14:06:57Z",
    "nvd_published_at" : null
  }
}