CVE-2011-2726 in Drupal
Summary
by MITRE
An access bypass issue was found in Drupal 7.x before version 7.5. If a Drupal site has the ability to attach File upload fields to any entity type in the system or has the ability to point individual File upload fields to the private file directory in comments, and the parent node is denied access, non-privileged users can still download the file attached to the comment if they know or guess its direct URL.
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Analysis
by VulDB Data Team • 01/12/2025
The vulnerability identified as CVE-2011-2726 represents a critical access control bypass issue within the Drupal content management system affecting versions 7.x prior to 7.5. This flaw specifically targets the file access control mechanisms that govern how uploaded files are handled within the system. The vulnerability arises from a design oversight in the permission checking logic that fails to properly validate access rights when files are attached to comment entities, creating a pathway for unauthorized users to bypass intended security controls.
The technical implementation of this vulnerability stems from how Drupal handles file access permissions when files are associated with comment entities. When a site administrator configures file upload fields to be attached to comment entities or explicitly points these fields to the private file directory, the system should enforce strict access controls. However, the flaw allows non-privileged users to circumvent these controls by directly accessing file URLs, even when the parent node or comment is restricted to authorized users only. This occurs because the permission checking mechanism does not properly validate whether the user has appropriate access rights to the file itself, rather than just the comment or node containing it.
The operational impact of this vulnerability is significant as it enables unauthorized data access and potential information disclosure. Attackers can exploit this flaw by discovering or guessing the direct URLs of files attached to comments, thereby gaining access to content that should be restricted to specific user roles or permissions. This vulnerability directly impacts the confidentiality and integrity of sensitive data stored within Drupal systems, particularly in environments where private file directories are used to store restricted content. The attack vector is relatively straightforward, requiring only knowledge of URL patterns or successful guessing of file paths, making it particularly dangerous in environments with predictable URL structures.
This vulnerability maps to CWE-284, which describes improper access control, and aligns with ATT&CK technique T1078.004 for valid accounts and T1566.001 for spearphishing attachments, as it enables unauthorized access to files through bypassing intended access controls. The flaw demonstrates a critical gap in the application's security model where file access permissions are not consistently enforced across all contexts where files are referenced. Organizations using Drupal systems with comment-based file attachments or private file directory configurations are particularly vulnerable, as the vulnerability can be exploited without requiring elevated privileges or complex attack chains. The remediation approach requires updating to Drupal version 7.5 or later, where the access control logic has been properly implemented to validate file permissions independently of the parent comment or node access rights.