CVE-2025-55009 in authkit-remix
Summary
by MITRE • 08/09/2025
The AuthKit library for Remix provides convenient helpers for authentication and session management using WorkOS & AuthKit with Remix. In versions 0.14.1 and below, @workos-inc/authkit-remix exposed sensitive authentication artifacts — specifically sealedSession and accessToken — by returning them from the authkitLoader. This caused them to be rendered into the browser HTML.
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Analysis
by VulDB Data Team • 08/12/2025
The vulnerability identified as CVE-2025-55009 affects the AuthKit library for Remix, a popular authentication helper framework that integrates with WorkOS and AuthKit for session management. This security flaw exists in versions 0.14.1 and earlier, where the library improperly handles sensitive authentication data during the authentication process. The issue stems from the authkitLoader function's implementation which inadvertently exposes critical session artifacts to client-side rendering, creating a significant security risk for applications utilizing this authentication framework.
The technical flaw manifests through the improper handling of sealedSession and accessToken objects within the authkitLoader function. These authentication artifacts contain sensitive session information that should remain server-side and never be transmitted to or rendered within browser HTML output. When the authkitLoader returns these values directly, they become embedded in the HTML response sent to clients, making them accessible through browser developer tools or network inspection. This represents a classic case of sensitive data exposure in client-side rendered applications, where server-side authentication tokens are unintentionally leaked to end users.
The operational impact of this vulnerability is substantial as it creates multiple attack vectors for malicious actors. The exposed accessToken and sealedSession values could potentially be used to impersonate users, gain unauthorized access to protected resources, or escalate privileges within applications using the affected AuthKit versions. Attackers could leverage these exposed credentials to perform session hijacking attacks, especially if the tokens contain sufficient privilege information or if they can be used to make authenticated API calls against backend services. The vulnerability essentially undermines the entire authentication mechanism by making server-side session management data available to client-side execution environments where it should remain protected.
This vulnerability aligns with CWE-200, which addresses "Information Exposure," and specifically relates to CWE-540, "Information Exposure Through Persistent Storage," and CWE-352, "Cross-Site Request Forgery," as it involves the exposure of sensitive data that could be exploited in various attack scenarios. From an ATT&CK framework perspective, this vulnerability maps to T1566, "Phishing," and T1531, "Account Access Removal," as it enables attackers to gain unauthorized access through the exposure of authentication tokens. The flaw also connects to T1071.004, "Application Layer Protocol: DNS," if the tokens are used in DNS-related authentication contexts, and T1078, "Valid Accounts," as it provides access to valid authentication artifacts.
Organizations using affected versions of the AuthKit library should immediately upgrade to version 0.14.2 or later, which implements proper isolation of sensitive authentication data. The recommended mitigation strategy involves ensuring that authkitLoader functions do not return sensitive session artifacts directly to client-side rendering contexts. Security teams should also implement comprehensive monitoring for any signs of unauthorized access attempts, conduct thorough code reviews to identify similar data exposure patterns, and consider implementing additional authentication layer protections such as token binding or short-lived access tokens. Organizations should also review their application's session management policies and ensure that sensitive data is properly sanitized before any HTML rendering occurs. The vulnerability demonstrates the critical importance of proper data handling in authentication frameworks and the potential consequences of failing to isolate sensitive server-side data from client-side execution environments.