CVE-2015-3175 in Moodle
Summary
by MITRE
Multiple open redirect vulnerabilities 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 allow remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via vectors involving an error page that links to a URL from an HTTP Referer header.
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Analysis
by VulDB Data Team • 05/19/2022
The CVE-2015-3175 vulnerability represents a critical open redirect flaw discovered in Moodle learning management systems across multiple version branches including 2.5.9 and earlier, 2.6.x versions prior to 2.6.11, 2.7.x versions before 2.7.8, and 2.8.x versions before 2.8.6. This vulnerability falls under the CWE-601 category of URL Redirects or Forwards, specifically targeting the improper validation of redirect URLs within the application's error handling mechanisms. The flaw exploits the system's reliance on the HTTP Referer header to determine redirect destinations, creating a dangerous pathway for malicious actors to manipulate user navigation. Security researchers identified that when Moodle encounters certain error conditions, it processes the Referer header to construct redirect URLs without proper sanitization or validation, allowing attackers to craft malicious URLs that would be executed as legitimate redirects within the application context.
The technical implementation of this vulnerability occurs through the error page handling mechanism where the application accepts and processes the HTTP Referer header value directly in redirect operations. When users encounter error pages, Moodle attempts to redirect them back to their previous location or a specified URL, but fails to validate that the target URL originates from the same domain or meets security requirements. This creates a scenario where an attacker can craft a malicious Referer header containing a crafted URL that points to a phishing site or malicious content, and when the error page is displayed, the user gets redirected to this attacker-controlled destination. The vulnerability is particularly dangerous because it leverages the trust relationship between the web browser and the application, where the browser automatically includes the Referer header with every request, making it easy for attackers to exploit without requiring user interaction beyond visiting a malicious page.
The operational impact of CVE-2015-3175 extends beyond simple redirection attacks, creating significant security risks for educational institutions and organizations relying on Moodle platforms. Attackers can utilize this vulnerability to conduct sophisticated phishing campaigns by redirecting users to credential harvesting pages that closely mimic legitimate Moodle interfaces, potentially compromising user accounts and gaining unauthorized access to sensitive educational data. The vulnerability also enables man-in-the-middle attack scenarios where users might be redirected to malicious sites that appear to be legitimate Moodle pages, allowing attackers to capture session tokens, personal information, or course materials. Organizations using affected Moodle versions face potential data breaches, unauthorized access to student records, and compromise of institutional security infrastructure, particularly since Moodle is widely used in academic environments where sensitive information such as grades, personal details, and research data are stored.
Mitigation strategies for CVE-2015-3175 require immediate implementation of security patches and configuration changes to prevent the exploitation of open redirect vulnerabilities. Organizations should upgrade to patched versions of Moodle, specifically versions 2.6.11, 2.7.8, and 2.8.6, which contain fixes addressing the improper URL validation in error handling mechanisms. System administrators should implement strict input validation for all redirect operations, ensuring that redirect URLs are validated against a whitelist of trusted domains or properly sanitized to prevent inclusion of external URLs. The implementation of Content Security Policy headers can provide additional protection by restricting the sources from which redirects can originate, while also implementing proper logging and monitoring of redirect operations to detect potential abuse. Security teams should also consider implementing network-level controls and web application firewalls to block suspicious Referer header values and monitor for patterns indicative of open redirect exploitation attempts, aligning with ATT&CK technique T1566.001 for Phishing and T1071.004 for Application Layer Protocol. Regular security assessments and vulnerability scanning should be conducted to ensure that similar vulnerabilities are not present in other components of the Moodle ecosystem or related applications.