CVE-2026-0948: Drupal Entra ID SSO Auth Bypass Flaw

CVE-2026-0948 Overview

An Authentication Bypass Using an Alternate Path or Channel vulnerability has been identified in the Drupal Microsoft Entra ID SSO Login module. This security flaw allows attackers to bypass the normal authentication flow and escalate privileges within affected Drupal installations.

The vulnerability is classified under CWE-288 (Authentication Bypass Using an Alternate Path or Channel), indicating that the module fails to properly secure all authentication pathways, allowing malicious actors to circumvent security controls through alternative routes that weren't adequately protected.

Critical Impact

Attackers can bypass SSO authentication mechanisms and escalate privileges, potentially gaining unauthorized administrative access to Drupal sites using Microsoft Entra ID for single sign-on authentication.

Affected Products

• Microsoft Entra ID SSO Login module for Drupal versions 0.0.0 through 1.0.3
• Drupal installations utilizing the vulnerable Microsoft Entra ID SSO Login module
• Web applications integrated with the affected SSO authentication flow

Discovery Timeline

• February 4, 2026 - CVE-2026-0948 published to NVD
• February 5, 2026 - Last updated in NVD database

Technical Details for CVE-2026-0948

Vulnerability Analysis

This authentication bypass vulnerability exists in the Drupal Microsoft Entra ID SSO Login module, which facilitates single sign-on functionality using Microsoft Entra ID (formerly Azure Active Directory). The vulnerability allows attackers to circumvent the intended authentication pathway by exploiting an alternate channel that lacks proper security validation.

Authentication bypass vulnerabilities of this nature typically occur when applications implement multiple authentication paths but fail to apply consistent security controls across all entry points. In this case, the SSO Login module appears to have an unprotected or insufficiently protected authentication route that can be exploited to achieve privilege escalation.

The network-accessible nature of this vulnerability means attackers can exploit it remotely without requiring prior authentication or user interaction, making it particularly dangerous for internet-facing Drupal installations.

Root Cause

The root cause of CVE-2026-0948 lies in the incomplete implementation of authentication controls within the Microsoft Entra ID SSO Login module. Specifically, the module version prior to 1.0.4 contains an alternate authentication path or channel that does not properly validate user credentials or session tokens, allowing attackers to bypass the primary SSO authentication mechanism.

This type of vulnerability often stems from:

• Incomplete coverage of authentication checks across all code paths
• Legacy or debugging endpoints that remain accessible in production
• Improper handling of authentication state transitions
• Insufficient validation of OAuth/OIDC tokens or callbacks

Attack Vector

The attack vector for this vulnerability is network-based, requiring no authentication or user interaction. An attacker with network access to a vulnerable Drupal installation can craft requests that exploit the alternate authentication channel.

The exploitation flow typically involves:

1. Reconnaissance: Identifying Drupal sites using the Microsoft Entra ID SSO Login module
2. Bypass Initiation: Sending crafted requests to the alternate authentication path
3. Token Manipulation: Exploiting the weak validation to establish an authenticated session
4. Privilege Escalation: Leveraging the bypassed authentication to access elevated functionality

Due to the sensitive nature of this vulnerability, specific exploitation details are not provided. Technical details can be found in the Drupal Security Advisory.

Detection Methods for CVE-2026-0948

Indicators of Compromise

• Unusual authentication patterns in Drupal access logs without corresponding Microsoft Entra ID login events
• User sessions created without associated SSO callback requests
• Administrative actions performed by accounts that lack proper SSO authentication trails
• Anomalous requests to SSO-related endpoints with malformed or missing authentication tokens

Detection Strategies

• Monitor Drupal authentication logs for sessions established without proper SSO workflow completion
• Implement correlation rules between Microsoft Entra ID audit logs and Drupal authentication events
• Deploy web application firewall rules to detect manipulation of SSO authentication parameters
• Review watchdog logs for authentication-related errors or warnings from the openid_connect or azure_entra_id modules

Monitoring Recommendations

• Enable verbose logging for the Microsoft Entra ID SSO Login module to capture authentication flow details
• Configure alerts for privilege escalation events, particularly when new administrator accounts are created
• Monitor for unusual patterns in authentication timing that may indicate bypass attempts
• Implement session correlation monitoring between the identity provider and Drupal application

How to Mitigate CVE-2026-0948

Immediate Actions Required

• Update the Microsoft Entra ID SSO Login module to version 1.0.4 or later immediately
• Audit all user accounts created or modified since the module was deployed for unauthorized privilege escalation
• Review authentication logs for evidence of exploitation attempts
• Consider temporarily disabling the SSO module if immediate patching is not possible

Patch Information

The vulnerability has been addressed in Microsoft Entra ID SSO Login version 1.0.4. Organizations should update to this version or later to remediate the vulnerability.

For detailed patch information and additional guidance, refer to the Drupal Security Advisory SA-CONTRIB-2026-005.

To update the module via Composer:

composer update drupal/azure_entra_id_sso_login
drush updatedb
drush cache:rebuild

Workarounds

• Disable the Microsoft Entra ID SSO Login module temporarily until the patch can be applied
• Implement network-level access controls to restrict access to SSO authentication endpoints
• Enable additional authentication factors or secondary verification for administrative actions
• Deploy web application firewall rules to filter suspicious authentication requests

# Temporary module disable via Drush (if patching is not immediately possible)
drush pm:uninstall azure_entra_id_sso_login

# Verify module is disabled
drush pm:list --type=module --status=disabled | grep azure