CVE-2016-9838 in Joomla
Summary
by MITRE
An issue was discovered in components/com_users/models/registration.php in Joomla! before 3.6.5. Incorrect filtering of registration form data stored to the session on a validation error enables a user to gain access to a registered user's account and reset the user's group mappings, username, and password, as demonstrated by submitting a form that targets the `registration.register` task.
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Analysis
by VulDB Data Team • 09/15/2024
The vulnerability identified as CVE-2016-9838 represents a critical security flaw in Joomla! version 3.6.4 and earlier, specifically within the user registration component. This issue resides in the file components/com_users/models/registration.php and stems from inadequate input validation during the user registration process. The flaw manifests when the system fails to properly sanitize or filter user-supplied data that gets stored in the session upon validation errors, creating a pathway for unauthorized account manipulation.
The technical implementation of this vulnerability exploits the session storage mechanism within Joomla's user registration workflow. When a user submits a registration form and validation fails, the system stores the submitted data in the session for later retrieval. However, the filtering process is insufficient, allowing malicious input to persist in the session state. This improper handling enables attackers to manipulate session data to gain unauthorized access to existing user accounts, effectively bypassing normal authentication mechanisms.
From an operational perspective, this vulnerability presents a severe risk to Joomla! installations as it allows attackers to reset user group mappings, usernames, and passwords without proper authentication. The attack vector specifically targets the registration.register task, which means an attacker could potentially compromise legitimate user accounts and assume their privileges. The impact extends beyond simple account takeover to include potential privilege escalation and data compromise, as group mappings control access levels within the application.
The vulnerability aligns with CWE-20, "Improper Input Validation," and represents a classic case of insufficient data sanitization in web applications. It also maps to ATT&CK technique T1078.004, "Valid Accounts: Cloud Accounts," as it enables unauthorized access through legitimate user account manipulation. The flaw demonstrates poor input handling practices where user-supplied data is not adequately validated before being stored in session variables, creating a persistent security risk.
Mitigation strategies for CVE-2016-9838 require immediate patching of Joomla framework.
The remediation process must include thorough testing of the patched version to ensure that legitimate registration functionality remains intact while the security vulnerability is eliminated. System administrators should also review and update their security monitoring procedures to detect potential exploitation attempts, particularly focusing on unusual session data patterns and registration form submissions that might indicate attempted exploitation of this vulnerability.