Auth0-PHP SDK Insecure Deserialization Vulnerability Allowing Unauthenticated Cookie Manipulation

A critical vulnerability has been identified in the Auth0-PHP SDK, specifically in versions 8.0.0-BETA3 prior to 8.3.1. This vulnerability arises from insecure deserialization of cookie data. The issue allows a threat actor to send a specially crafted cookie containing malicious serialized data. Since the SDK processes cookie content without prior authentication, this vulnerability can be exploited in applications using Auth0-PHP, as well as those relying on Auth0/symfony, Auth0/laravel-auth0, or Auth0/wordpress SDKs, which depend on vulnerable Auth0-PHP versions.

Impact

Exploitation of this vulnerability could lead to unauthorized manipulation of cookie data, allowing for potential injection of malicious serialized objects into the application.

Reproduction

To reproduce this vulnerability, set up an application using the Auth0-PHP SDK version 8.0.0-BETA3 prior to 8.3.1. Alternatively, use an application that relies on the Auth0-PHP SDK within the vulnerable version range, such as those using the Auth0/symfony, Auth0/laravel-auth0, or Auth0/wordpress SDKs. Once the application is running, send a crafted cookie that includes malicious serialized data. The application will process the cookie without authentication, triggering the vulnerability.

Remediation

Upgrade the Auth0-PHP SDK to version 8.3.1 or later. For applications using Auth0/symfony, Auth0/laravel-auth0, or Auth0/wordpress, ensure to update to the latest versions of those SDKs, which have incorporated the necessary patch.