CVE-2013-5674 in Moodle
Summary
by MITRE
badges/external.php in Moodle 2.5.x before 2.5.2 does not properly handle an object obtained by unserializing a description of an external badge, which allows remote attackers to conduct PHP object injection attacks via unspecified vectors, as demonstrated by overwriting the value of the userid parameter.
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Analysis
by VulDB Data Team • 12/24/2024
The vulnerability identified as CVE-2013-5674 resides within Moodle's external badge handling mechanism, specifically in the badges/external.php file of Moodle versions 2.5.x prior to 2.5.2. This flaw represents a critical security weakness that enables remote attackers to exploit PHP object injection vulnerabilities through improperly sanitized user input. The vulnerability stems from the application's failure to adequately validate and sanitize serialized data when processing external badge descriptions, creating an attack surface where malicious actors can manipulate object serialization patterns to execute arbitrary code.
The technical implementation of this vulnerability occurs when Moodle processes external badge data through the unserialize() function without proper input validation. This creates a classic PHP object injection scenario where an attacker can craft malicious serialized data that, when unserialized, executes unintended code within the application context. The specific exploitation vector demonstrated in this case involves manipulation of the userid parameter, allowing attackers to overwrite critical user identification values and potentially escalate privileges or gain unauthorized access to user accounts. This vulnerability aligns with CWE-502 which categorizes deserialization of untrusted data as a significant security risk, particularly when involving object-oriented programming languages like PHP.
The operational impact of CVE-2013-5674 extends beyond simple data manipulation, as it provides attackers with potential pathways for privilege escalation and persistent access within Moodle environments. Organizations using affected Moodle versions face risks including unauthorized user account access, data theft, and potential compromise of entire learning management systems. The vulnerability's remote nature means that attackers do not require physical access to the system, making it particularly dangerous for educational institutions and organizations relying on web-based learning platforms. Attackers can leverage this weakness to manipulate user sessions, access sensitive course materials, and potentially establish backdoors for continued unauthorized access.
Mitigation strategies for this vulnerability require immediate patching of affected Moodle installations to version 2.5.2 or later, which includes proper input validation and sanitization of serialized data. Organizations should implement network-level protections including firewall rules that restrict access to external badge endpoints and monitor for suspicious serialization patterns in system logs. Additionally, security measures should include regular vulnerability assessments of Moodle plugins and custom code, implementation of web application firewalls, and comprehensive user access controls. The remediation process should also involve reviewing all external badge configurations and ensuring that only trusted sources are permitted to provide badge data. This vulnerability demonstrates the critical importance of proper input validation in web applications and aligns with ATT&CK technique T1548.005 which covers privilege escalation through object injection attacks. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain comprehensive incident response procedures for potential exploitation attempts.