CVE-2015-3176 in Moodle
Summary
by MITRE
The account-confirmation feature in login/confirm.php in Moodle through 2.5.9, 2.6.x before 2.6.11, 2.7.x before 2.7.8, and 2.8.x before 2.8.6 allows remote attackers to obtain sensitive full-name information by attempting to self-register.
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Analysis
by VulDB Data Team • 05/19/2022
The vulnerability described in CVE-2015-3176 represents a critical information disclosure flaw within Moodle's account confirmation mechanism. This issue affects multiple versions of the popular learning management system, specifically targeting the login/confirm.php script that handles user registration and account verification processes. The vulnerability stems from insufficient input validation and output sanitization during the self-registration workflow, creating an exploitable condition that allows remote attackers to extract sensitive user information without proper authentication or authorization.
The technical flaw manifests in the account confirmation feature where the system fails to properly validate or sanitize user inputs during the registration process. When users attempt to self-register, the system inadvertently reveals full name information through error messages or response handling mechanisms. This occurs because the confirmation script does not adequately verify the legitimacy of registration attempts or properly handle edge cases in user input processing. The vulnerability operates under CWE-200, which classifies it as an information disclosure weakness, specifically related to insufficient output sanitization and improper error handling.
From an operational perspective, this vulnerability poses significant risks to user privacy and system security. Attackers can exploit this flaw to enumerate user accounts and gather personal information including full names, which can then be used for social engineering attacks, credential stuffing attempts, or targeted phishing campaigns. The impact extends beyond simple information disclosure as it enables attackers to build profiles of system users, potentially leading to more sophisticated attacks. This vulnerability directly violates the principle of least privilege and can be categorized under ATT&CK technique T1087.001 for account discovery, as it allows unauthorized enumeration of valid user accounts.
The exploitation of this vulnerability requires minimal technical skill and can be automated, making it particularly dangerous in environments with large user bases. Attackers can systematically attempt registration with various email addresses and observe the system responses to identify valid accounts and extract associated full names. This type of attack can be conducted without requiring any prior access credentials or system compromise, making it a low-hanging fruit for threat actors. The vulnerability's persistence across multiple version lines indicates a fundamental flaw in the input validation and error handling mechanisms that should have been addressed through proper security code review processes.
Organizations using affected Moodle versions should implement immediate mitigations including updating to patched versions, implementing rate limiting on registration attempts, and strengthening input validation mechanisms. The recommended approach involves applying the vendor-provided security patches that address the specific validation gaps in the confirmation script. Additionally, system administrators should review and harden the registration process to prevent information leakage through error messages and implement proper access controls to limit the exposure of user account information. Security monitoring should be enhanced to detect unusual registration patterns that may indicate exploitation attempts, and network-level controls can be implemented to restrict access to registration endpoints from suspicious sources.