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CVE-2025-43865: React Router allows pre-render data spoofing on React-Router framework mode

• Severity: high (CVSS 8.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-04-25 · updated 2026-06-17
• Weakness: CWE-345

Description

React Router is a router for React. In versions on the 7.0 branch prior to version 7.5.2, it's possible to modify pre-rendered data by adding a header to the request. This allows to completely spoof its contents and modify all the values ​​of the data object passed to the HTML. This issue has been patched in version 7.5.2.

Affected products

• remix-run react-router: from 7.0, < 7.5.2

References

• https://github.com/remix-run/react-router/blob/e6c53a0130559b4a9bd47f9cf76ea5b08a69868a/packages/react-router/lib/server-runtime/routes.ts#L87
• https://github.com/remix-run/react-router/commit/c84302972a152d851cf5dd859ff332b354b70111
• https://github.com/remix-run/react-router/security/advisories/GHSA-cpj6-fhp6-mr6j

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