CVE-2026-40181

React Router's same-origin redirect with path starting // causes open redirect via protocol-relative URL reinterpretation

Description

Certain URLs passed to the redirect function can trigger an open redirect to an external domain depending on the level of validation done by the application prior to returning the redirect.

[!NOTE] This does not impact your React Router application if you are using Declarative Mode (<BrowserRouter>)

Patch Available

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

Fix without upgrading

Score

6.6

Severity

Medium

Ecosystem

JavaScript

Publish Date

June 3, 2026

Modified Date

June 9, 2026

Score Vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U

Affected Versions