CVE-2017-17068 in auth0.js Library
Summary
by MITRE
A cross-origin vulnerability has been discovered in the Auth0 auth0.js library affecting versions < 8.12. This vulnerability allows an attacker to acquire authenticated users' tokens and invoke services on a user's behalf if the target site or application uses a popup callback page with auth0.popup.callback().
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Analysis
by VulDB Data Team • 12/12/2019
The vulnerability identified as CVE-2017-17068 represents a critical cross-origin resource sharing issue within the Auth0 auth0.js library ecosystem. This flaw specifically impacts versions prior to 8.12 and stems from improper handling of cross-origin communication mechanisms within the authentication flow. The vulnerability manifests when applications utilize the auth0.popup.callback() method, which creates a security gap that can be exploited by malicious actors to manipulate the authentication process. The core issue lies in the library's failure to properly validate the origin of callback messages, allowing unauthorized domains to intercept and utilize legitimate authentication tokens.
The technical exploitation of this vulnerability occurs through a sophisticated cross-origin attack vector that leverages the popup-based authentication mechanism. When users authenticate through a popup window, the auth0.js library establishes communication channels between different origins without adequate origin verification. Attackers can craft malicious websites that trick users into interacting with the authentication popup, subsequently capturing the authentication tokens that are meant to be restricted to the legitimate application domain. This cross-origin information leakage directly violates fundamental security principles of web application isolation and authentication token protection. The vulnerability aligns with CWE-346, which addresses "Origin Validation Error", and represents a classic example of insufficient validation of a cross-origin request.
The operational impact of this vulnerability extends beyond simple token theft, as it enables full authentication bypass capabilities for attackers. Once an attacker successfully captures a user's authentication token through this cross-origin exploit, they can invoke services on behalf of the authenticated user without requiring additional credentials. This unauthorized access can lead to complete account compromise, data exfiltration, and privilege escalation within the application ecosystem. The attack vector is particularly dangerous because it requires minimal user interaction beyond visiting a malicious website, making it a significant threat to applications that rely heavily on OAuth 2.0 and OpenID Connect authentication flows. The vulnerability also aligns with ATT&CK technique T1566, which covers "Phishing for Information", as it exploits the trust relationship between the user and the authentication system.
Mitigation strategies for CVE-2017-17068 require immediate library version updates to 8.12 or later, where Auth0 implemented proper origin validation mechanisms. Organizations should also review their authentication flows to minimize reliance on popup-based callbacks when possible, instead implementing redirect-based authentication mechanisms that provide better security boundaries. Additional protective measures include implementing Content Security Policy headers to restrict cross-origin communication, utilizing secure authentication libraries that properly handle cross-origin scenarios, and conducting regular security audits of authentication components. The vulnerability demonstrates the critical importance of proper cross-origin resource validation in modern web applications and highlights the need for comprehensive security testing of third-party libraries that handle sensitive authentication data.