---
id: CVE-2026-53666
aliases:
  - GHSA-337j-9hxr-rhxg
title: >-
  React Router: Arbitrary Constructor Injection via deserializeErrors() in React
  Router SSR Hydration
summary: >-
  React Router: Arbitrary Constructor Injection via deserializeErrors() in React
  Router SSR Hydration
severity: medium
cvss: 6.1
cwe:
  - CWE-470
vendor: react-router
product: react-router
ecosystem: npm
affected:
  - 'react-router >= 6.4.0, < 7.18.0'
patched:
  - react-router 7.18.0
published: '2026-07-23'
updated: '2026-07-23'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-337j-9hxr-rhxg'
references:
  - url: >-
      https://github.com/remix-run/react-router/security/advisories/GHSA-337j-9hxr-rhxg
  - url: 'https://github.com/remix-run/react-router/pull/15175'
  - url: >-
      https://github.com/remix-run/react-router/commit/9d22943fd46c8ae4b08236425fa3549e10e9ad1a
  - url: 'https://github.com/remix-run/react-router/blob/main/CHANGELOG.md#v7180'
  - url: 'https://github.com/remix-run/react-router/releases/tag/react-router@7.18.0'
  - url: 'https://github.com/advisories/GHSA-337j-9hxr-rhxg'
tags:
  - ghsa
  - npm
ingestedAt: '2026-07-23T20:19:19.570Z'
epss: 0.0042
epssPercentile: 0.33631
---

## Overview

If application code allows attacker supplied input to overwrite certain aspects of errors caught by the SSR process, then it was possible for attacker to trigger unexpected constructor execution on the client which would trigger outbound network traffic.  This is only possible with very specific (and unlikely) application layer code.

> [!NOTE]
> This does not impact your application if you are using Declarative Mode.  This only impacts Framework Mode and Data Mode applications doing manual SSR/hydration

## Affected packages

- `react-router >= 6.4.0, < 7.18.0`

## Remediation

Upgrade to a patched release:

- `react-router 7.18.0`