CVE-2025-55008 is a high-severity vulnerability affecting versions 0.6.1 and below of the @workos-inc/authkit-react-router library, which is used to facilitate authentication and session management in React Router 7+ applications integrating WorkOS and AuthKit. The vulnerability arises from the library's authkitLoader function returning sensitive authentication artifacts—specifically the sealedSession and accessToken—directly to the client-side by rendering them into the browser's HTML. This exposure constitutes an information disclosure flaw classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). Because these tokens are critical for authenticating users and maintaining session integrity, their exposure can allow attackers to hijack user sessions or impersonate users without needing additional credentials. The CVSS 3.1 base score of 7.1 reflects a high severity, with the vector indicating network attack vector (AV:N), high attack complexity (AC:H), low privileges required (PR:L), no user interaction (UI:N), unchanged scope (S:U), and high impact on confidentiality and integrity (C:H/I:H) with low impact on availability (A:L). The vulnerability does not require user interaction but does require some level of privilege, likely meaning an attacker needs to be able to trigger or access the vulnerable endpoint. The issue was fixed in version 0.7.0 by preventing the sensitive tokens from being exposed in the client-rendered HTML. No known exploits are currently reported in the wild, but the nature of the vulnerability makes it a critical concern for applications relying on this library for authentication.

For European organizations using the affected versions of authkit-react-router, this vulnerability poses a significant risk to user data confidentiality and session integrity. Attackers who can access the exposed tokens may impersonate legitimate users, leading to unauthorized access to sensitive systems and data. This can result in data breaches, regulatory non-compliance (notably with GDPR), reputational damage, and potential financial losses. Since the tokens are exposed in the browser HTML, any attacker capable of intercepting or viewing the rendered page (e.g., via cross-site scripting, man-in-the-middle attacks on unsecured connections, or compromised user devices) could exploit this vulnerability. Organizations in sectors with high compliance requirements such as finance, healthcare, and government are particularly at risk. The vulnerability could also facilitate lateral movement within enterprise environments if session tokens grant access to internal resources. Given the widespread use of React and WorkOS in modern web applications, the scope of affected systems could be broad, especially for SaaS providers and enterprises leveraging these technologies for authentication.

European organizations should immediately audit their applications to identify any usage of @workos-inc/authkit-react-router versions below 0.7.0. The primary mitigation is to upgrade to version 0.7.0 or later, where the vulnerability is fixed. Additionally, organizations should review their deployment and build processes to ensure that no sensitive tokens are inadvertently exposed in client-side code or HTML. Implementing strict Content Security Policies (CSP) can help mitigate the risk of token theft via cross-site scripting. Network-level protections such as enforcing HTTPS with HSTS can prevent man-in-the-middle attacks that might capture exposed tokens. Organizations should also consider implementing short-lived tokens and token revocation mechanisms to limit the window of exploitation if tokens are compromised. Monitoring for unusual authentication patterns or session anomalies can help detect exploitation attempts. Finally, educating developers about secure handling of authentication artifacts and conducting regular security code reviews will reduce the risk of similar issues.