CVE-2014-7835 in Moodle
Summary
by MITRE
webservice/upload.php in Moodle 2.6.x before 2.6.6 and 2.7.x before 2.7.3 does not ensure that a file upload is for a private or draft area, which allows remote authenticated users to upload files containing JavaScript, and consequently conduct cross-site scripting (XSS) attacks, by specifying the profile-picture area.
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Analysis
by VulDB Data Team • 04/04/2022
The vulnerability identified as CVE-2014-7835 affects Moodle learning management systems version 2.6.x prior to 2.6.6 and 2.7.x prior to 2.7.3, specifically within the webservice/upload.php component. This issue represents a critical security flaw that undermines the platform's file upload validation mechanisms, creating an avenue for malicious exploitation through cross-site scripting attacks. The vulnerability stems from insufficient validation of file upload destinations, particularly concerning the profile-picture area designation that should typically restrict uploads to private or draft contexts.
The technical flaw manifests in the improper handling of file upload parameters where the system fails to verify whether an upload operation targets a private or draft area before processing the file. This omission allows authenticated users to manipulate the upload process by specifying the profile-picture area, which typically should be restricted to private user contexts. When combined with the ability to upload files containing JavaScript code, this creates a direct pathway for executing malicious scripts within the browser context of other users who view the uploaded content. The vulnerability operates under CWE-20, which describes improper input validation, specifically in the context of file upload restrictions and access control mechanisms.
The operational impact of this vulnerability extends beyond simple XSS execution, as it enables attackers to compromise user sessions and potentially escalate privileges within the Moodle environment. Remote authenticated users can leverage this flaw to inject malicious JavaScript into profile pictures, which then executes when other users view these images. This creates a persistent threat vector that can be used for session hijacking, data exfiltration, or further exploitation of the Moodle platform. The attack requires only legitimate user authentication, making it particularly dangerous as it can be exploited through normal user accounts without requiring administrative privileges or additional authentication.
Security professionals should note that this vulnerability aligns with ATT&CK technique T1566.001, which involves social engineering through spearphishing with a link, as the malicious JavaScript can be delivered through seemingly legitimate profile picture uploads. The remediation strategy centers on implementing proper access control validation within the file upload service, ensuring that all upload operations verify the target area's permissions before processing. Organizations should immediately upgrade to Moodle versions 2.6.6 or 2.7.3 and subsequently implement additional security measures including input sanitization, file type validation, and comprehensive access control checks for all file upload operations. The fix requires modification of the upload.php script to enforce strict validation of upload destinations and ensure that only authorized areas accept file uploads, particularly those designated for public or shared contexts.