What’s Vulnerable › Vulnerabilities

CVE-2026-55685: React Router: Unauthenticated Denial of Service via Inefficient Route Matching

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-27 · updated 2026-10-24
• Weakness: CWE-400

Description

React Router is a router for React. In versions 7.0.0 through 7.17.0, the manifest endpoint could be accessed via unauthenticated targeted requests that would put heavy load on the server and slow down response times. This issue is a follow up to CVE-2026-42342, and does not does not impact React Router applications using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>). This issue has been fixed in version 7.18.0.

Affected products

• remix-run react-router: from 7.0.0 before 7.18.0 — fixed in 7.18.0

How to fix

Upgrade to a fixed version: remix-run react-router 7.18.0. Check the vendor advisory for mitigations.

References

• https://github.com/remix-run/react-router/blob/main/CHANGELOG.md#v7180
• https://github.com/remix-run/react-router/commit/09e6020d1950e54f361f7ad00938ecd4dde60929
• https://github.com/remix-run/react-router/pull/15186
• https://github.com/remix-run/react-router/releases/tag/react-router@7.18.0
• https://github.com/remix-run/react-router/security/advisories/GHSA-8x6r-g9mw-2r78
• https://github.com/remix-run/react-router/security/advisories/GHSA-chx6-hx7r-mcp5

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