CVE-2025-12466: Drupal Simple OAuth Auth Bypass Flaw

CVE-2025-12466 Overview

CVE-2025-12466 is an Authentication Bypass Using an Alternate Path or Channel vulnerability (CWE-288) affecting the Drupal Simple OAuth (OAuth2) & OpenID Connect module. This vulnerability allows attackers to bypass authentication mechanisms by exploiting an alternate path or channel within the authentication flow, potentially gaining unauthorized access to protected resources without proper credentials.

Critical Impact

Attackers can bypass authentication controls in Drupal installations using the Simple OAuth module, potentially gaining unauthorized access to sensitive data and protected API endpoints.

Affected Products

• Drupal Simple OAuth (OAuth2) & OpenID Connect versions 6.0.0 through 6.0.6
• Drupal-based applications utilizing the Simple OAuth module for OAuth2 authentication
• Systems implementing OpenID Connect authentication via the affected module

Discovery Timeline

• 2025-10-30 - CVE-2025-12466 published to NVD
• 2025-12-04 - Last updated in NVD database

Technical Details for CVE-2025-12466

Vulnerability Analysis

This vulnerability exists in the authentication logic of the Simple OAuth module for Drupal, which provides OAuth2 and OpenID Connect functionality. The flaw allows attackers to bypass the standard authentication pathway by utilizing an alternate channel that does not properly enforce authentication requirements. When exploited, this vulnerability enables unauthorized access to confidential information without requiring valid credentials.

The network-accessible nature of this vulnerability means it can be exploited remotely without user interaction or prior privileges, making it particularly dangerous for internet-facing Drupal installations. The primary impact is on confidentiality, as successful exploitation allows unauthorized disclosure of protected information.

Root Cause

The root cause of CVE-2025-12466 is an Authentication Bypass Using an Alternate Path or Channel (CWE-288). This occurs when the authentication logic fails to consistently validate credentials across all possible access paths. In the Simple OAuth module, an alternate authentication channel exists that does not properly enforce the same security controls as the primary authentication mechanism, allowing attackers to circumvent the intended authentication flow.

Attack Vector

The attack vector for CVE-2025-12466 is network-based, requiring no user interaction or prior authentication. An attacker can exploit this vulnerability by:

1. Identifying Drupal installations running vulnerable versions of the Simple OAuth module
2. Crafting requests that utilize the alternate authentication path
3. Bypassing standard OAuth2/OpenID Connect authentication flows
4. Gaining unauthorized access to protected resources and sensitive data

The vulnerability manifests in the authentication handling logic of the Simple OAuth module. Technical details regarding the specific bypass mechanism can be found in the Drupal Security Advisory.

Detection Methods for CVE-2025-12466

Indicators of Compromise

• Unusual authentication patterns or OAuth token requests that bypass standard login flows
• Access to protected API endpoints without corresponding valid authentication events
• Anomalous OAuth2/OpenID Connect authorization requests with malformed or missing parameters
• Unexpected access to user data or protected resources without proper session establishment

Detection Strategies

• Monitor OAuth2 token generation and validation logs for anomalous authentication patterns
• Implement Web Application Firewall (WAF) rules to detect authentication bypass attempts
• Review Drupal access logs for unauthorized access to protected endpoints
• Enable and monitor detailed OAuth/OpenID Connect authentication logging

Monitoring Recommendations

• Configure alerting for authentication failures followed by successful resource access
• Monitor for unusual patterns in OAuth token issuance and validation
• Implement real-time log analysis for Drupal authentication events
• Track API endpoint access patterns for anomalies indicating authentication bypass

How to Mitigate CVE-2025-12466

Immediate Actions Required

• Upgrade Drupal Simple OAuth module to version 6.0.7 or later immediately
• Audit access logs for signs of exploitation prior to patching
• Review OAuth token issuance logs for any suspicious authentication patterns
• Invalidate existing OAuth tokens as a precautionary measure after upgrading

Patch Information

The Drupal security team has released version 6.0.7 of the Simple OAuth module to address this vulnerability. Organizations should apply this update immediately to remediate the authentication bypass vulnerability. For detailed patch information and upgrade instructions, refer to the Drupal Security Advisory SA-CONTRIB-2025-114.

Workarounds

• Implement additional authentication layers at the web server or reverse proxy level
• Restrict network access to OAuth2/OpenID Connect endpoints to trusted IP ranges
• Deploy a Web Application Firewall (WAF) with rules to detect and block authentication bypass attempts
• Consider temporarily disabling the Simple OAuth module if it is not critical to operations until patching is complete

# Update Simple OAuth module via Composer
composer update drupal/simple_oauth --with-dependencies

# Clear Drupal caches after update
drush cache:rebuild

# Verify installed version
drush pm:list --filter=simple_oauth