CVE-2017-6922 in Drupal
Summary
by MITRE
In Drupal core 8.x prior to 8.3.4 and Drupal core 7.x prior to 7.56; Private files that have been uploaded by an anonymous user but not permanently attached to content on the site should only be visible to the anonymous user that uploaded them, rather than all anonymous users. Drupal core did not previously provide this protection, allowing an access bypass vulnerability to occur. This issue is mitigated by the fact that in order to be affected, the site must allow anonymous users to upload files into a private file system.
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Analysis
by VulDB Data Team • 07/05/2024
The vulnerability described in CVE-2017-6922 represents a critical access bypass flaw in Drupal core versions prior to 8.3.4 and 7.56. This issue specifically affects the handling of private file uploads by anonymous users within Drupal's file system architecture. The fundamental problem lies in the improper implementation of access control mechanisms that should have restricted file visibility to only the user who originally uploaded the file. According to CWE-284, this vulnerability manifests as an inadequate access control implementation where the system fails to properly enforce authorization checks for file resources. The flaw creates a scenario where anonymous users can potentially access files that were intended to remain private to the specific anonymous uploader, thereby violating the principle of least privilege that is essential for secure file management systems.
The technical implementation of this vulnerability stems from Drupal's file system handling logic where private files uploaded by anonymous users were not properly isolated from other anonymous users. In a properly functioning system, each anonymous file upload should be associated with a unique session identifier or user context that prevents other anonymous users from accessing those files. However, the vulnerability allowed for cross-access between anonymous file uploads, effectively creating a pathway for unauthorized information disclosure. This issue directly relates to ATT&CK technique T1213 which involves data from information repositories, specifically targeting the exposure of private data through improper access controls. The vulnerability operates at the application layer where the file access control mechanisms fail to properly validate user permissions against file ownership, creating a persistent access bypass condition that remains active until the affected Drupal versions are patched.
The operational impact of this vulnerability is significant for organizations running Drupal sites that permit anonymous file uploads in private file systems. Attackers exploiting this vulnerability could gain access to sensitive information that was intended to remain private to individual anonymous uploaders, potentially including personal documents, confidential attachments, or other restricted content. The risk is particularly elevated for sites that host user-generated content where anonymous uploads are permitted, as these systems become vulnerable to information disclosure attacks. Organizations may experience reputational damage, compliance violations, and potential legal consequences if sensitive data becomes accessible to unauthorized parties through this access bypass mechanism. The vulnerability also creates opportunities for attackers to gather intelligence about site usage patterns and user behavior through the exposure of private file content.
Mitigation strategies for CVE-2017-6922 focus on immediate version upgrades to Drupal core 8.3.4 or 7.56, which contain the necessary patches to properly enforce access controls for anonymous file uploads. Organizations should also implement additional security measures such as disabling anonymous file uploads where possible, configuring proper file system permissions, and monitoring file access logs for suspicious activity. The patch addresses the core access control implementation by ensuring that private files uploaded by anonymous users are properly associated with the specific upload context and are not accessible to other anonymous users. Security teams should conduct comprehensive vulnerability assessments of their Drupal installations to identify any remaining instances of the vulnerability and implement proper access control auditing. Additionally, organizations should review their file system configurations to ensure that private file storage directories are properly secured and that session management for anonymous users is appropriately implemented to prevent similar access bypass scenarios in other components of their Drupal environment.