CVE-2025-67848: Moodle Auth Bypass Vulnerability

CVE-2025-67848 Overview

A critical authentication bypass vulnerability has been discovered in Moodle's Learning Tools Interoperability (LTI) Provider functionality. This flaw allows suspended users to circumvent access restrictions and successfully authenticate through the LTI authentication handlers. The vulnerability stems from the LTI authentication mechanism failing to properly validate and enforce the user's suspension status during the authentication process.

When exploited, this vulnerability enables users who have been administratively suspended from the Moodle platform to regain unauthorized access. This bypass can lead to unauthorized information disclosure, data manipulation, or other malicious actions that suspended users should be restricted from performing.

Critical Impact

Suspended users can bypass access controls via LTI authentication, potentially accessing sensitive course materials, student data, and other protected resources they should no longer have access to.

Affected Products

• Moodle LMS with LTI Provider enabled
• Moodle installations utilizing LTI authentication workflows
• Organizations using Moodle with external LTI tool integrations

Discovery Timeline

• 2026-02-03 - CVE-2025-67848 published to NVD
• 2026-02-03 - Last updated in NVD database

Technical Details for CVE-2025-67848

Vulnerability Analysis

This authentication bypass vulnerability (CWE-280: Improper Handling of Insufficient Permissions or Privileges) occurs within Moodle's LTI Provider authentication flow. The LTI authentication handlers process incoming authentication requests from external LTI consumers but fail to check whether the authenticating user has been suspended from the Moodle system.

Under normal circumstances, when a user is suspended in Moodle, their access to the platform is revoked, and they should be unable to log in or access any resources. However, the LTI authentication pathway operates independently and does not query the user's suspension status before granting access tokens or completing the authentication handshake.

This creates a security gap where suspended users can leverage LTI tool launches from external platforms to bypass the front-door suspension check and gain authenticated sessions within Moodle. Once authenticated, these users may access course content, view student information, submit assignments, or perform other actions depending on their original role permissions.

Root Cause

The root cause of this vulnerability lies in the incomplete implementation of access control checks within the LTI authentication handlers. The authentication logic validates credentials and establishes user identity but omits the critical step of verifying the user's account status (specifically the suspended flag) before completing authentication. This oversight allows the authentication to succeed even when the user's account has been administratively disabled.

The LTI Provider module processes authentication separately from Moodle's standard login mechanisms, and the suspension check that exists in the main login flow was not replicated in the LTI authentication path.

Attack Vector

An attacker who has been suspended from a Moodle instance can exploit this vulnerability by initiating an LTI tool launch from an external Learning Management System or LTI consumer that has a trust relationship with the vulnerable Moodle installation. The attack requires:

1. The attacker must have previously had a valid account on the target Moodle instance
2. The attacker's account must have been suspended (not deleted)
3. The Moodle instance must have LTI Provider functionality enabled
4. The attacker must have access to an external LTI consumer configured to communicate with the target Moodle

The vulnerability is network-exploitable and requires low privileges, as the attacker only needs their previously valid suspended credentials. No user interaction is required beyond the attacker initiating the LTI launch.

Detection Methods for CVE-2025-67848

Indicators of Compromise

• Successful LTI authentication events associated with user accounts marked as suspended in the Moodle database
• Access logs showing activity from users whose suspension date precedes the access timestamp
• Unusual course access or data retrieval by accounts that should have restricted access
• LTI launch requests completing successfully for users with suspended = 1 in the mdl_user table

Detection Strategies

• Implement log correlation rules to cross-reference successful LTI authentications against the user suspension status in real-time
• Create database queries to identify any access records from suspended users within LTI-related tables
• Monitor for authentication anomalies where users bypass standard login flows through LTI endpoints
• Review LTI Provider logs for authentication patterns involving previously active but now suspended accounts

Monitoring Recommendations

• Enable detailed logging for the LTI Provider module including user identifiers for all authentication attempts
• Configure alerts for successful authentications where the associated user account has a non-zero suspension flag
• Audit LTI consumer configurations and limit trusted external systems to reduce attack surface
• Regularly review access logs for suspended user accounts across all authentication pathways

How to Mitigate CVE-2025-67848

Immediate Actions Required

• Review the Moodle Discussion Post #471298 for official guidance and patches
• Audit LTI authentication logs to identify any potential exploitation by suspended users
• Consider temporarily disabling LTI Provider functionality if it is not critical to operations
• Review and verify all currently suspended user accounts for any unauthorized access

Patch Information

Moodle users should consult the official security advisories for patch availability. Additional details can be found in the Red Hat CVE-2025-67848 Advisory and Red Hat Bug #2423831. Apply the latest security updates from Moodle as soon as they become available to remediate this vulnerability.

Workarounds

• Disable the LTI Provider functionality in Moodle settings until patches are applied: navigate to Site Administration → Plugins → Authentication → Manage authentication and disable LTI authentication
• Implement network-level restrictions to limit access to LTI endpoints from trusted IP addresses only
• Convert suspended accounts to fully deleted accounts where appropriate to eliminate the authentication bypass pathway
• Configure web application firewall rules to monitor and potentially block suspicious LTI authentication requests

# Configuration example - Disable LTI Provider authentication via CLI
php admin/cli/cfg.php --component=auth_lti --name=enabled --set=0

# Alternative: Review suspended users with LTI access
mysql -e "SELECT id, username, email, suspended, timecreated FROM mdl_user WHERE suspended = 1;"