CVE-2016-2403 in Symfony
Summary
by MITRE
Symfony before 2.8.6 and 3.x before 3.0.6 allows remote attackers to bypass authentication by logging in with an empty password and valid username, which triggers an unauthenticated bind.
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Analysis
by VulDB Data Team • 02/19/2020
The vulnerability identified as CVE-2016-2403 affects Symfony frameworks version 2.8.6 and earlier, as well as version 3.0.6 and earlier, presenting a critical authentication bypass flaw that enables remote attackers to gain unauthorized system access. This vulnerability specifically targets the authentication mechanism within Symfony's security component, where the framework fails to properly validate user credentials when an empty password is submitted alongside a valid username. The flaw operates by exploiting a weakness in the authentication binding process that occurs during login attempts.
The technical implementation of this vulnerability stems from improper input validation within Symfony's authentication system, where the framework does not adequately check for empty password values during the authentication process. When a user attempts to log in with a valid username but an empty password field, the system performs an unauthenticated bind operation that bypasses normal security checks. This behavior creates a condition where any valid username can be used to establish a connection without proper authentication, effectively allowing unauthorized access to protected resources. The vulnerability is classified under CWE-287, which addresses improper authentication issues in software systems.
The operational impact of CVE-2016-2403 is severe and far-reaching, as it allows attackers to bypass authentication mechanisms entirely without requiring valid credentials. This flaw enables remote attackers to access sensitive system resources, potentially leading to data breaches, privilege escalation, and unauthorized system modifications. The vulnerability particularly affects web applications built on Symfony framework that implement user authentication, making it a significant concern for organizations relying on this popular PHP framework. Attackers can exploit this issue to gain access to user accounts, administrative panels, and other protected system components without detection, as the system does not properly validate the authentication attempt.
Security practitioners should immediately implement mitigations including upgrading to Symfony versions 2.8.6 or later, or 3.0.6 and later, which contain the necessary patches to address this authentication bypass vulnerability. Organizations should also conduct comprehensive security assessments of their Symfony applications to identify potential exposure to this flaw. Additional defensive measures include implementing proper input validation for authentication endpoints, monitoring login attempts for unusual patterns, and ensuring that authentication systems properly validate all credential inputs. The vulnerability aligns with ATT&CK technique T1078 which covers valid accounts and privilege escalation through authentication bypass methods. Regular security updates and vulnerability management processes are essential to prevent exploitation of this and similar authentication-related vulnerabilities in web applications.