CVE-2012-6087 in PHP
Summary
by MITRE
repository/s3/S3.php in the Amazon S3 library in Moodle through 2.2.11, 2.3.x before 2.3.9, 2.4.x before 2.4.6, and 2.5.x before 2.5.2 does not verify that the server hostname matches a domain name in the subject s Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate, related to an incorrect CURLOPT_SSL_VERIFYHOST value.
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Analysis
by VulDB Data Team • 04/22/2021
The vulnerability described in CVE-2012-6087 represents a critical SSL certificate validation flaw within Moodle's Amazon S3 storage integration. This issue affects multiple versions of the Moodle learning management system, specifically those through 2.2.11, 2.3.x before 2.3.9, 2.4.x before 2.4.6, and 2.5.x before 2.5.2. The core problem lies in the improper implementation of SSL certificate verification within the S3.php library, which is responsible for handling Amazon S3 storage operations within the Moodle platform.
The technical flaw stems from the incorrect configuration of the CURLOPT_SSL_VERIFYHOST option in the underlying cURL library implementation. This parameter controls how strictly SSL certificates are validated against the server's hostname. When set to an incorrect value, typically zero or false, the system fails to perform proper hostname verification against the certificate's Common Name (CN) field or Subject Alternative Name (SAN) fields. This misconfiguration allows attackers to conduct successful man-in-the-middle attacks by presenting any valid SSL certificate, regardless of whether it matches the target server's domain name. The vulnerability specifically targets the SSL/TLS certificate validation process, which is fundamental to establishing secure communications between Moodle and Amazon S3 storage services.
The operational impact of this vulnerability is severe and multifaceted. Attackers can exploit this weakness to intercept, modify, or redirect data transmitted between Moodle and Amazon S3 storage, potentially compromising sensitive educational data including student records, grades, assignments, and course materials. The vulnerability enables attackers to impersonate legitimate S3 servers, making it particularly dangerous in environments where Moodle stores confidential information. This flaw undermines the entire security model of the platform's cloud storage integration, potentially allowing unauthorized access to academic content and user data. The implications extend beyond simple data theft, as attackers could also modify course content, grades, or user permissions, leading to significant educational and administrative disruptions.
This vulnerability maps directly to CWE-295, which addresses "Improper Certificate Validation," and aligns with ATT&CK technique T1046 for network service scanning and T1566 for credential access through social engineering. The improper SSL certificate validation creates a pathway for attackers to establish false trust relationships with the Moodle system. Organizations using affected Moodle versions face substantial risk of data breaches, regulatory compliance violations, and reputational damage. The vulnerability demonstrates the critical importance of proper SSL/TLS implementation in web applications and highlights the need for robust certificate validation mechanisms. Security practitioners should prioritize immediate patching of affected Moodle installations and implement additional monitoring for suspicious network activity between Moodle systems and Amazon S3 services. The issue also underscores the necessity of following security best practices for SSL certificate validation, including proper configuration of SSL_VERIFYHOST and SSL_VERIFYPEER parameters in all web applications that communicate with external services.