CVE-2026-40181

React Router's same-origin redirect with path starting // causes open redirect via protocol-relative URL reinterpretation

Certain URLs passed to the redirect function can trigger an open redirect to an external domain depending on the level of validation done by the application prior to returning the redirect.

[!NOTE]
This does not impact your React Router application if you are using Declarative Mode (<BrowserRouter>)

Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites. Typical impact: phishing and credential harvesting via a trusted domain.

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1. What is CVE-2026-40181? CVE-2026-40181 is a medium-severity open redirect vulnerability in react-router (npm), affecting versions >= 7.0.0, < 7.14.1. It is fixed in 7.14.1, 6.30.4, 1.23.3. Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites.
2. Which packages are affected by CVE-2026-40181?
   • react-router (npm) (versions >= 7.0.0, < 7.14.1)
   • @remix-run/router (npm) (versions >= 1.3.0, < 1.23.3)
3. Is there a fix for CVE-2026-40181? Yes. CVE-2026-40181 is fixed in 7.14.1, 6.30.4, 1.23.3. Upgrade to this version or later.
4. Is CVE-2026-40181 exploitable, and should I be worried? Whether CVE-2026-40181 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-40181 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-40181?
   • Upgrade react-router to 7.14.1 or later
   • Upgrade react-router to 6.30.4 or later
   • Upgrade @remix-run/router to 1.23.3 or later

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