CVE-2015-3272 in Moodle
Summary
by MITRE
Open redirect vulnerability in the clean_param function in lib/moodlelib.php in Moodle through 2.6.11, 2.7.x before 2.7.9, 2.8.x before 2.8.7, and 2.9.x before 2.9.1 allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via vectors involving an HTTP Referer header that has a substring match with a local URL.
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Analysis
by VulDB Data Team • 05/31/2022
The CVE-2015-3272 vulnerability represents a critical open redirect flaw within the Moodle learning management system that affects multiple versions including 2.6.11 and below, 2.7.x versions prior to 2.7.9, 2.8.x versions before 2.8.7, and 2.9.x versions before 2.9.1. This vulnerability resides in the clean_param function located within the lib/moodlelib.php file, which serves as a fundamental component for parameter sanitization and validation throughout the Moodle platform. The flaw specifically exploits how the system handles HTTP Referer headers during parameter processing, creating a pathway for malicious actors to manipulate user redirection behavior.
The technical implementation of this vulnerability stems from improper validation of HTTP Referer headers within the clean_param function. When Moodle processes user input, it performs substring matching against local URLs to determine if a redirect should occur. Attackers can craft malicious Referer headers containing substrings that match legitimate local URLs, thereby bypassing the intended security checks. This allows the system to accept and process redirect requests that would normally be rejected, enabling attackers to redirect users to arbitrary external websites. The vulnerability operates under CWE-601, which specifically addresses URL redirection and forwarding vulnerabilities, making it a direct implementation of this well-known security weakness. The flaw essentially creates a trust relationship between the application and user-provided data that should never exist, as the system incorrectly validates user-controlled input as legitimate.
The operational impact of this vulnerability is significant and multifaceted, particularly in educational environments where Moodle platforms handle sensitive user data and credentials. Attackers can leverage this vulnerability to conduct sophisticated phishing campaigns by redirecting users to malicious websites that appear legitimate within the context of the Moodle interface. The attack vector becomes particularly dangerous when combined with social engineering tactics, as users may not immediately recognize that they have been redirected to a fraudulent site. The vulnerability enables man-in-the-middle attacks, credential harvesting, and data exfiltration attempts, potentially compromising not just individual user accounts but entire institutional databases. This opens the door to broader security breaches that could affect student records, administrative data, and sensitive academic information, making it a critical concern for educational institutions relying on Moodle platforms.
Mitigation strategies for CVE-2015-3272 require immediate patching of affected Moodle versions to the latest stable releases that contain the necessary security fixes. Organizations should implement comprehensive input validation measures that do not rely on substring matching for redirect decisions, instead employing strict URL validation that verifies complete URLs against predefined safe domains. Network-level protections such as web application firewalls should be configured to monitor and block suspicious Referer header patterns that could indicate exploitation attempts. Security teams should also implement regular vulnerability scanning procedures that specifically target open redirect vulnerabilities in web applications. The implementation of Content Security Policy headers and proper HTTP header controls can provide additional defense-in-depth measures. Organizations should also conduct security awareness training for administrators to recognize potential exploitation patterns and establish monitoring procedures that can detect unusual redirect behavior within their Moodle environments. This vulnerability demonstrates the importance of proper input validation and the potential consequences of trusting user-provided data in security-critical functions, aligning with ATT&CK techniques that emphasize credential access and initial access through web application vulnerabilities.