CVE-2026-33244

React Router has stored XSS via unescaped Location header in prerendered redirect HTML

Description

When using React Router v7 Framework Mode with Pre-rendering enabled, an improper neutralization of the HTTP Location header value can permit Cross-Site Scripting (XSS) in statically generated HTML files if the redirect location comes from an untrusted source.

[!NOTE] This does not impact your React Router application if you are using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>).

Patch Available

Fix available through Seal Security. No upgrade required, protect your application instantly.

Fix without upgrading

Score

5.4

Severity

Medium

Ecosystem

JavaScript

Publish Date

June 3, 2026

Modified Date

June 3, 2026

Score Vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Affected Versions