CVE-2025-55008 in authkit-react-router
Summary
by MITRE • 08/09/2025
The AuthKit library for React Router 7+ provides helpers for authentication and session management using WorkOS & AuthKit with React Router. In versions 0.6.1 and below, @workos-inc/authkit-react-router exposed sensitive authentication artifacts — specifically sealedSession and accessToken by returning them from the authkitLoader. This caused them to be rendered into the browser HTML. This issue is fixed in version 0.7.0.
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Analysis
by VulDB Data Team • 08/12/2025
The vulnerability described in CVE-2025-55008 affects the AuthKit library for React Router 7+, which serves as a authentication and session management helper integrating with WorkOS and AuthKit. This library is designed to facilitate secure authentication flows within React applications that utilize React Router for navigation. The flaw manifests in versions 0.6.1 and earlier where the authkitLoader function inadvertently exposes sensitive authentication artifacts to the client-side application. The specific sensitive data includes sealedSession and accessToken values that are returned by the loader function, creating a direct pathway for authentication credentials to be accessible within the browser's rendered HTML output.
The technical nature of this vulnerability stems from improper handling of authentication tokens within the server-side rendering context. When the authkitLoader function returns authentication artifacts directly to the client, these sensitive values become embedded in the HTML response that gets delivered to the browser. This exposure occurs because the loader function, which is intended to prepare authentication data for the client, fails to properly sanitize or remove sensitive information before returning it. The sealedSession and accessToken values represent critical security tokens that, when exposed in client-side HTML, could be extracted by malicious actors through various means including browser developer tools, network monitoring, or cross-site scripting attacks. This represents a classic case of information disclosure vulnerability where sensitive data is unintentionally made available to unauthorized parties.
The operational impact of this vulnerability is significant as it directly compromises the security of authentication flows within affected applications. When authentication tokens are rendered into browser HTML, they become accessible to any user with access to the browser's developer console or network traffic inspection tools. Attackers could potentially extract these tokens and use them to impersonate legitimate users, gain unauthorized access to protected resources, or perform session hijacking attacks. The vulnerability affects applications using React Router 7+ with the AuthKit library, making it particularly concerning for modern web applications that rely heavily on client-side routing and authentication. The exposure of sealedSession tokens is especially dangerous as these typically contain encrypted session information that, when compromised, could allow attackers to forge valid sessions and bypass authentication mechanisms entirely.
The fix implemented in version 0.7.0 addresses this vulnerability by modifying the authkitLoader function to properly handle sensitive authentication data. This update ensures that authentication artifacts are not directly returned to the client-side application and instead are processed in a manner that prevents their exposure in rendered HTML. Organizations using affected versions should immediately upgrade to version 0.7.0 or later to mitigate this risk. The vulnerability aligns with CWE-200 (Information Exposure) and represents a failure in proper input validation and output sanitization. From an ATT&CK perspective, this vulnerability maps to T1566 (Phishing) and T1531 (Account Access Removal) as it enables adversaries to obtain authentication credentials that can then be used for unauthorized access to protected resources. The remediation approach should include thorough code review of authentication flows, implementation of proper token handling procedures, and regular security testing of authentication libraries to prevent similar exposure issues in the future.