CVE-2011-4294 in Moodle
Summary
by MITRE
The error-message functionality in Moodle 1.9.x before 1.9.13, 2.0.x before 2.0.4, and 2.1.x before 2.1.1 does not ensure that a continuation link refers to an http or https URL for the local Moodle instance, which might allow attackers to trick users into visiting arbitrary web sites via unspecified vectors.
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Analysis
by VulDB Data Team • 12/06/2021
The vulnerability described in CVE-2011-4294 represents a significant security flaw in the Moodle learning management system that affects multiple versions including 1.9.x before 1.9.13, 2.0.x before 2.0.4, and 2.1.x before 2.1.1. This issue resides within the error-message functionality of the platform, specifically concerning how continuation links are handled when displaying error messages to users. The flaw stems from inadequate validation of URL schemes in the continuation links that are presented to users during error conditions, creating a potential vector for malicious redirection attacks.
The technical implementation of this vulnerability allows attackers to manipulate the continuation links that appear in error messages, potentially enabling them to redirect users to external malicious websites while maintaining the appearance of legitimate Moodle navigation. This type of vulnerability falls under the category of open redirect vulnerabilities, which are classified as CWE-601 in the Common Weakness Enumeration system. The flaw specifically exploits the lack of proper URL validation mechanisms that should ensure all continuation links point to valid http or https resources within the local Moodle instance rather than allowing arbitrary external URLs to be specified.
From an operational perspective, this vulnerability creates a serious risk for Moodle deployments as it can be exploited to conduct phishing attacks, social engineering campaigns, or other malicious activities that leverage user trust in the Moodle platform. When users encounter error messages and click on continuation links, they may be unknowingly redirected to attacker-controlled websites that could attempt to harvest credentials, install malware, or perform other malicious activities. The unspecified vectors mentioned in the description suggest that the attack could be executed through various means including crafted error conditions, manipulated session data, or other input manipulation techniques that cause the system to generate malicious continuation links.
The impact of this vulnerability extends beyond simple redirection as it undermines the fundamental trust users place in the Moodle platform's security. Attackers can exploit this weakness to create convincing phishing scenarios that appear legitimate due to the error message context, making users more susceptible to falling for social engineering attacks. Organizations using affected Moodle versions face potential data breaches, credential theft, and reputational damage if this vulnerability is exploited successfully. The vulnerability also demonstrates poor input validation practices that should be addressed through proper security coding standards and input sanitization mechanisms.
Effective mitigation strategies for this vulnerability include applying the official security patches released by Moodle for the affected versions, which typically involve implementing proper URL scheme validation in error message handling components. Organizations should also consider implementing additional security measures such as content security policies, web application firewalls, and monitoring for suspicious redirection patterns. The remediation process should include thorough testing to ensure that error message functionality properly validates all continuation links and rejects any that do not conform to the expected http or https protocols within the local Moodle instance. This vulnerability serves as a reminder of the importance of proper input validation and URL handling in web applications, aligning with ATT&CK technique T1566 for social engineering attacks and emphasizing the need for robust security controls in educational platforms that handle sensitive user data.