CVE-2026-53666

React Router: Arbitrary Constructor Injection via deserializeErrors() in React Router SSR Hydration

React Router is a router for React. In versions 6.4.0 through 7.17.0, if application code was written in a way that allows attacker-supplied input to overwrite certain aspects of errors caught by the SSR process, then it was possible for an attacker to trigger unexpected constructor execution on the client, which would in turn trigger an outbound network request. This is only possible with very specific (and unlikely) application-layer code. Note that this does not impact an application if it is using Declarative Mode. It only impacts Framework Mode and Data Mode applications that perform manual SSR/hydration. This issue has been fixed in version 7.18.0.

We have discovered 625 live websites that are affected by CVE-2026-53666.

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Affected Software

Product  React Router DOM
Category JavaScript Libraries
Vulnerable Domains625 live websites (67% of React Router DOM install base)
Vulnerable Versions
  • from 6.4 through 7.18
Vulnerable Versions Count39 versions ( 67% of all versions)


Common Weakness Enumeration

CWE-470 Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')



Details

  • Published - Jul 27, 2026
  • Updated - Jul 28, 2026

Website Distribution by Country

Number of websites using CVE-2026-53666
United States235 websites


New Zealand225 websites
Germany47 websites
Singapore10 websites
Russia9 websites
Brazil8 websites
France8 websites
Japan8 websites
Cyprus7 websites
Netherlands7 websites

Website Distribution by TLD

Number of websites using CVE-2026-53666
.com227 websites
.net14 websites
.com.br12 websites
.ru9 websites
.org8 websites
.co7 websites
.de7 websites
.nl5 websites
.com.au5 websites
.co.uk4 websites

Vulnerable Versions

Vulnerable versions are highlighted in red

Websites affected by CVE-2026-53666

Top websites that are affected by CVE-2026-53666. Please click on the "Contact us" link to get more information.
DomainCountryRankContacts
**********.com United States**,***
***.com United States**,***
***.com United States**,***
*****.com United States**,***
****.com United States**,***
*********.com United States***,***
*******.com United States***,***
*****.org United States***,***
******.cz United States***,***
*****.jp Japan***,***
See full domain list

FAQ

CVE-2026-53666 is Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') in React Router DOM
A total of 625 websites have been identified as vulnerable to CVE-2026-53666, based on global website indexing conducted by WebTechSurvey.
The React Router DOM is affected by the CVE-2026-53666 vulnerability.
React Router DOM versions up to 7.18 are vulnerable to CVE-2026-53666.
CVE-2026-53666 is resolved in version 7.18 of React Router DOM.