Packages / react-router / Security

ModerateVulnerabilityGHSA-337j-9hxr-rhxgCVE-2026-53666Published 23 Jul 2026

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

Affected releases · react-router

  • 7.x7.0.0 – 7.17.0Fixed in 7.18.0
  • 6.x6.4.0 – 6.30.6No fix on this line yet

On 7.x, the newest line:

npm install react-router@7.18.0
8.x

  1. Not affected

    8.0.0 – 8.5.0

    8 releases, latest

7.x

  1. Affected

    7.0.0 – 7.17.0

    47 releases

  2. Fixed

    7.18.0 – 7.18.4

    5 releases

6.x

  1. Not affected

    6.0.0 – 6.3.0

    9 releases

  2. Affected

    6.4.0 – 6.30.6

    61 releases

228 stable releases of react-router, oldest to newest, one row per major.

Is your project affected?

Paste your package.json, or type the range you declare for react-router. It is read in your browser and sent nowhere.

What happens

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