CVE-2026-40181 React Router's same-origin redirect with path starting // causes open redirect via protocol-relative URL reinterpretation
Attackers can exploit protocol-relative URL handling in React Router to redirect users to external domains, bypassing same-origin restrictions.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40181?
CVE-2026-40181 is a medium-severity vulnerability in @remix-run/router, published on 2 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
React Router is a router for React. In versions 7.0.0 through 7.14.0 and 6.7.0 through 6.30.3, certain URLs passed to the redirect function can trigger an open redirect to an external domain due to path values starting with // being reinterpreted as protocol-relative URLs. The level of impact depends on the validation done by the application prior to returning the redirect. This does not impact applications using Declarative Mode (<BrowserRouter>). This is patched in versions 7.14.1 and 6.30.4.
Weakness: CWE-601
Which versions are affected by CVE-2026-40181?
6 open source packages ship an affected version, including @remix-run/router and react-router. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
@remix-run/router npm | From 1.3.0 | 1.23.3 |
@remix-run/router npm | From 1.3.0 | 1.23.3 |
react-router npm | From 6.7.0 | 6.30.4 |
react-router npm | From 6.7.0 | 6.30.4 |
react-router npm | From 7.0.0 | 7.14.1 |
react-router npm | From 7.0.0 | 7.14.1 |
Products include Shopify React-Router.
How do I fix CVE-2026-40181?
Upgrade @remix-run/router to 1.23.3 or later.
Is CVE-2026-40181 being exploited?
There is no known exploitation of CVE-2026-40181 in the wild and no public exploit code.
Other vulnerabilities in @remix-run/router
- CVE-2026-55685 React Router: Unauthenticated Denial of Service via Inefficient Route Matching
- CVE-2026-21884 React Router SSR XSS in ScrollRestoration
- CVE-2026-42211 React Router's vendored turbo-stream v2 allows arbitrary constructor invocation via TYPE_ERROR deserialization leading to Unauth RCE
- CVE-2026-33245 React Router vulnerable to XSS in unstable RSC redirect handling via javascript: redirect targets
- CVE-2026-22029 React Router vulnerable to XSS via Open Redirects
Sources
Also known as CLSA-2026-1788255151, CLSA-2026-1789597929, CLSA-2026-1792253404, CLSA-2026-1792419117, CLSA-2026-1792419192, CLSA-2026-1792419271 and 12 more.