CVE-2010-3091 in Drupal
Summary
by MITRE
The OpenID module in Drupal 6.x before 6.18, and the OpenID module 5.x before 5.x-1.4 for Drupal, violates the OpenID 2.0 protocol by not verifying the openid.return_to value, which allows remote attackers to bypass authentication by leveraging an assertion from an OpenID provider.
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Analysis
by VulDB Data Team • 09/25/2021
The vulnerability described in CVE-2010-3091 represents a critical security flaw in the OpenID authentication implementation within Drupal content management systems. This issue affects Drupal 6.x versions prior to 6.18 and Drupal 5.x versions prior to 5.x-1.4, specifically within the OpenID module that handles external authentication protocols. The flaw stems from the module's failure to properly validate the openid.return_to parameter during the OpenID authentication flow, creating a significant bypass opportunity for malicious actors seeking unauthorized access to Drupal sites.
The technical root cause of this vulnerability lies in the improper implementation of the OpenID 2.0 protocol specification. According to the OpenID 2.0 standard, the openid.return_to parameter must be strictly validated to ensure that the authentication response is being directed back to the legitimate originating URL. The Drupal OpenID module's failure to verify this parameter creates an authentication bypass condition where attackers can manipulate the return URL to redirect authentication responses to arbitrary locations. This validation gap allows remote attackers to craft malicious OpenID assertions that appear legitimate to the Drupal system but actually redirect users to unauthorized access points.
The operational impact of this vulnerability extends beyond simple authentication bypass, as it can enable attackers to gain unauthorized administrative access to Drupal sites. When users authenticate through compromised OpenID providers, the system accepts assertions without proper verification of the return URL, potentially allowing attackers to impersonate legitimate users or gain elevated privileges. This vulnerability directly maps to CWE-287, which addresses improper authentication issues, and aligns with ATT&CK technique T1078.004 for valid accounts, as it enables unauthorized access through manipulated authentication flows. The attack vector requires minimal privileges and can be executed remotely, making it particularly dangerous for web applications that rely on OpenID for user authentication.
Mitigation strategies for this vulnerability involve immediate patching of affected Drupal installations to versions 6.18 or 5.x-1.4 and higher, which contain the necessary fixes for proper OpenID return URL validation. Organizations should also implement additional security measures including monitoring for unauthorized authentication attempts, validating all OpenID provider configurations, and ensuring that OpenID authentication is properly configured with appropriate security controls. Network-level controls such as firewalls and intrusion detection systems can help detect anomalous authentication patterns, while application-level security measures should include strict validation of all external authentication parameters and regular security audits of authentication modules. The fix implemented in the patched versions ensures that the openid.return_to parameter is properly verified against the expected return URL, preventing attackers from manipulating the authentication flow to gain unauthorized access to Drupal sites.