CVE-2026-1106: Chamilo LMS Auth Bypass Vulnerability

CVE-2026-1106 Overview

A security vulnerability has been discovered in Chamilo LMS affecting versions up to 2.0.0 Beta 1. This improper authorization flaw exists in the deleteLegal function within the src/CoreBundle/Controller/SocialController.php file of the Legal Consent Handler component. By manipulating the userId argument, an attacker can bypass authorization controls, potentially allowing unauthorized deletion of legal consent records for other users.

Critical Impact

This improper authorization vulnerability allows authenticated remote attackers to manipulate legal consent data for arbitrary users, potentially compromising compliance records and user privacy settings in affected Chamilo LMS installations.

Affected Products

• Chamilo LMS up to 2.0.0 Beta 1
• Chamilo LMS Legal Consent Handler component
• src/CoreBundle/Controller/SocialController.php - deleteLegal function

Discovery Timeline

• 2026-01-18 - CVE-2026-1106 published to NVD
• 2026-01-18 - Last updated in NVD database

Technical Details for CVE-2026-1106

Vulnerability Analysis

This vulnerability is classified under CWE-266 (Incorrect Privilege Assignment), indicating a fundamental flaw in how the application handles authorization checks. The deleteLegal function in the SocialController fails to properly verify that the requesting user has appropriate privileges to delete legal consent records for the specified userId. This allows an authenticated attacker to perform actions on behalf of or affecting other users without proper authorization.

The attack can be carried out remotely over the network, requiring only low-level privileges (authenticated user access). The vulnerability primarily impacts the integrity and availability of legal consent data, allowing unauthorized modification or deletion of records.

Root Cause

The root cause of this vulnerability lies in insufficient authorization validation within the deleteLegal function. The function accepts a userId parameter but does not adequately verify that the authenticated user has permission to perform delete operations on records belonging to the specified user ID. This represents a classic Insecure Direct Object Reference (IDOR) pattern where user-supplied input is used to directly access objects without proper access control checks.

Attack Vector

The attack is network-based and requires an authenticated user account. An attacker can exploit this vulnerability by manipulating the userId parameter in requests to the deleteLegal endpoint. By substituting their own user ID with that of another user, the attacker can delete legal consent records belonging to other users.

The vulnerability affects the Legal Consent Handler component, which typically manages user agreements and compliance-related data. Successful exploitation could result in unauthorized deletion of legal consent records, potentially causing compliance violations and affecting audit trails.

According to the CVE description, an exploit has been publicly released and may be used for attacks. Technical details are available through the HXLab Resource Share and VulDB.

Detection Methods for CVE-2026-1106

Indicators of Compromise

• Unusual patterns of DELETE requests to the SocialController endpoints with varying userId parameters
• Multiple legal consent deletion operations originating from a single user session but targeting different user IDs
• Audit log entries showing consent record deletions that don't correlate with legitimate user actions
• Anomalous access patterns to /deleteLegal endpoints from authenticated sessions

Detection Strategies

• Implement web application firewall (WAF) rules to detect parameter tampering on userId fields in requests to the Legal Consent Handler
• Monitor application logs for authorization failures or unusual patterns in the SocialController.php component
• Deploy runtime application self-protection (RASP) solutions to detect and block IDOR exploitation attempts
• Review audit logs for bulk or automated deletion patterns targeting legal consent records

Monitoring Recommendations

• Enable verbose logging for all operations within the Legal Consent Handler component
• Set up alerts for multiple failed or successful legal consent operations across different user accounts within short time windows
• Monitor for requests to deleteLegal endpoints where the userId parameter differs from the authenticated session's user ID
• Implement anomaly detection for unusual access patterns to compliance-related endpoints

How to Mitigate CVE-2026-1106

Immediate Actions Required

• Restrict access to the Legal Consent Handler endpoints to only trusted administrative users until a patch is available
• Implement additional server-side authorization checks to verify user identity before processing deleteLegal requests
• Review and audit existing legal consent records for any signs of unauthorized modification or deletion
• Consider temporarily disabling the deleteLegal functionality if it is not critical to operations

Patch Information

At the time of publication, no official patch is available from the vendor. According to the vulnerability disclosure, the vendor was contacted but did not respond. Organizations should monitor the official Chamilo LMS repository and security advisories for updates. Additional vulnerability details can be found at VulDB #341698 and the VulDB Submission.

Workarounds

• Implement a web application firewall rule to validate that the userId parameter matches the authenticated user's session
• Apply application-level access controls to restrict the deleteLegal function to administrators only
• Deploy network segmentation to limit exposure of the Chamilo LMS instance to trusted networks
• Implement comprehensive logging and monitoring to detect exploitation attempts

# Example: Restricting access to SocialController endpoints via .htaccess
# Add to your Chamilo LMS .htaccess or Apache configuration
<LocationMatch "/social/deleteLegal">
    Require group admin
    # Or restrict by IP
    # Require ip 192.168.1.0/24
</LocationMatch>