CVE-2018-1045 in Moodle
Summary
by MITRE
In Moodle 3.x, there is XSS via a calendar event name.
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Analysis
by VulDB Data Team • 02/02/2023
The vulnerability CVE-2018-1045 represents a cross-site scripting flaw in Moodle version 3.x that specifically affects calendar event names. This issue arises from insufficient input validation and output encoding mechanisms within the calendar component of the learning management system. The vulnerability allows attackers to inject malicious scripts into calendar event names, which are then executed in the browsers of other users who view these events. The flaw demonstrates a classic lack of proper sanitization in web applications where user-supplied data is directly rendered without adequate security measures.
The technical implementation of this vulnerability stems from the way Moodle processes and displays calendar event data. When users create calendar events, the system accepts event names without sufficient sanitization of potentially dangerous characters or script tags. The calendar component fails to properly encode special characters in event names before rendering them in HTML contexts, creating an opportunity for attackers to inject malicious JavaScript code. This weakness falls under CWE-79 which specifically addresses cross-site scripting vulnerabilities due to improper input handling. The vulnerability exists because the application does not implement proper output encoding or input validation for user-generated content that is subsequently displayed in web interfaces.
The operational impact of this vulnerability extends beyond simple script execution as it can enable attackers to perform various malicious activities. An attacker could craft calendar events containing malicious scripts that steal session cookies, redirect users to phishing sites, or even execute commands on behalf of authenticated users. This poses significant risks to educational institutions using Moodle, as calendar events are frequently used for important announcements, assignments, and scheduling information. The vulnerability can be exploited by any user with permission to create calendar events, making it particularly dangerous in environments where multiple users have administrative or instructor privileges. The attack vector is relatively straightforward requiring only the ability to create calendar events with malicious content, which aligns with ATT&CK technique T1059.007 for command and script injection.
Mitigation strategies for CVE-2018-1045 should focus on implementing comprehensive input validation and output encoding mechanisms. Organizations should immediately upgrade to Moodle versions that have patched this vulnerability, as the official Moodle security team released updates addressing this specific issue. Additionally, administrators should implement strict input validation for all calendar event fields, including name, description, and location fields, ensuring that special characters are properly escaped or removed. The implementation of Content Security Policy headers can provide additional protection against script execution even if other defenses fail. Regular security audits of web applications should include testing for similar input validation vulnerabilities in calendar and event management components. Organizations should also consider implementing role-based access controls to limit calendar creation permissions to trusted users only, reducing the attack surface for potential exploitation. The vulnerability demonstrates the critical importance of input sanitization in web applications and serves as a reminder of the need for comprehensive security testing throughout the software development lifecycle.