What is CVE-2026-42211?

CVE-2026-42211 is a high-severity vulnerability in Remix-Run React-Router, classified under Deserialization of Untrusted Data. CVSS score: 8.1/10. Published 2026-06-02.

How severe is CVE-2026-42211?

High severity. CVSS v3 base score is 8.1 out of 10.

Deserialization in Remix-Run React-Router

CVE-2026-42211

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.

Vulnerability class: Insecure Deserialization

EPSS: 0.004 (35.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Remix-run React-router — versions >= 7.0.0, < 7.14.2
Shopify React-router

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

References

security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)

Frequently asked questions

What is CVE-2026-42211?: CVE-2026-42211 is a high-severity vulnerability in Remix-Run React-Router, classified under Deserialization of Untrusted Data. CVSS score: 8.1/10. Published 2026-06-02.
How severe is CVE-2026-42211?: High severity. CVSS v3 base score is 8.1 out of 10.