CVE-2026-42211 React Router's vendored turbo-stream v2 allows arbitrary constructor invocation via TYPE_ERROR deserialization leading to Unauth RCE
Attackers can achieve remote code execution in React Router Framework Mode via unsafe deserialization if prototype pollution exists.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42211?
CVE-2026-42211 is a high-severity unsafe deserialization vulnerability in remix-run react-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 7.14.1, when using Framework Mode, a combination of steps could potentially allow unauthorized remote code execution (RCE) through external requests. This attack requires the application code to have an existing prototype pollution vulnerability, which can then be leveraged in a 2-step attack where the second step triggers unauthorized RCE on the remote server. This does not impact applications using Declarative Mode (`<BrowserRouter>`) or Data Mode (`createBrowserRouter/<RouterProvider>`). This is patched in version 7.14.2.
Weakness: CWE-502
Which versions are affected by CVE-2026-42211?
2 open source packages ship an affected version, including react-router. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
react-router npm | From 7.0.0 | 7.14.2 |
react-router npm | From 7.0.0 | 7.14.2 |
Products include Shopify React-Router.
How do I fix CVE-2026-42211?
Upgrade react-router to 7.14.2 or later.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2026-42211 being exploited?
There is no known exploitation of CVE-2026-42211 in the wild and no public exploit code.
Other vulnerabilities in remix-run react-router
- CVE-2026-55685 React Router: Unauthenticated Denial of Service via Inefficient Route Matching
- CVE-2026-21884 React Router SSR XSS in ScrollRestoration
- CVE-2026-33245 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
- CVE-2025-59057 React Router has XSS Vulnerability
Sources
Also known as CLSA-2026-1784856365, CLSA-2026-1792192812, CLSA-2026-1792253397, CLSA-2026-1792253409, CLSA-2026-1792419112, CLSA-2026-1792419189 and 9 more.