This vulnerability, tracked as CVE-2026-22030, arises from improper origin validation in React Router and Remix frameworks, specifically in versions prior to 7.12.0 and 2.17.3 respectively. React Router is a widely used routing library for React applications, and Remix is a React framework that builds on it. The flaw allows attackers to perform Cross-Site Request Forgery (CSRF) attacks targeting document POST requests routed through server-side action handlers in Framework Mode or when using React Server Actions in unstable RSC modes. CSRF attacks exploit the trust a web application places in a user's browser, causing unintended actions on behalf of the user without their consent. The vulnerability is due to insufficient origin validation (CWE-346) and improper CSRF protections (CWE-352). Applications using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>) are not affected, as these modes handle routing differently and do not expose the vulnerable server-side action handlers. The CVSS v3.1 score of 6.5 reflects a medium severity, with network attack vector, low attack complexity, no privileges required, but requiring user interaction. The impact is primarily on integrity, allowing unauthorized state-changing requests. The issue was publicly disclosed on January 10, 2026, and patches are available in react-router 7.12.0 and @remix-run/server-runtime 2.17.3. No known exploits have been reported in the wild, but the vulnerability is significant for applications relying on the affected versions and modes.

For European organizations, this vulnerability poses a risk to web applications built with affected versions of React Router and Remix frameworks, especially those using server-side route action handlers in Framework Mode or React Server Actions. Successful exploitation could allow attackers to perform unauthorized state-changing operations, such as modifying user data or triggering transactions, without user consent. This can lead to data integrity issues, potential financial loss, reputational damage, and regulatory non-compliance under GDPR if personal data is affected. Since React is widely adopted in Europe for web development, organizations in sectors like finance, e-commerce, healthcare, and government services that use these frameworks are at risk. The requirement for user interaction means phishing or social engineering could be used to exploit the vulnerability. The absence of impact on Declarative or Data Mode users limits the scope somewhat, but organizations using Framework Mode or unstable RSC modes must prioritize remediation. The lack of known active exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits post-disclosure.

European organizations should immediately audit their web applications to identify usage of react-router versions between 7.0.0 and 7.11.0 or @remix-run/server-runtime versions below 2.17.3. Applications using Framework Mode or React Server Actions in unstable RSC modes require urgent attention. The primary mitigation is to upgrade to react-router 7.12.0 or later and @remix-run/server-runtime 2.17.3 or later, where the vulnerability is patched. For applications that cannot upgrade immediately, implementing strict CSRF protections such as synchronizer tokens or double-submit cookies on server-side POST handlers can reduce risk. Additionally, enforcing Content Security Policy (CSP) to restrict origins and employing SameSite cookies can help mitigate CSRF risks. Developers should review routing modes and consider migrating to Declarative or Data Mode if feasible, as these are not affected. Monitoring for unusual POST requests and user activity anomalies can provide early detection. Finally, educating users about phishing risks and ensuring secure development lifecycle practices will help prevent exploitation.