CVE-2017-6919 in Drupal
Summary
by MITRE
Drupal 8 before 8.2.8 and 8.3 before 8.3.1 allows critical access bypass by authenticated users if the RESTful Web Services (rest) module is enabled and the site allows PATCH requests.
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Analysis
by VulDB Data Team • 12/20/2020
The vulnerability identified as CVE-2017-6919 represents a critical access control flaw in Drupal 8 content management systems that affects versions prior to 8.2.8 and 8.3.1. This security issue specifically targets installations where the RESTful Web Services module is enabled and permits PATCH request operations, creating a significant risk for authenticated users who can exploit this weakness to gain unauthorized access to system resources. The vulnerability falls under the category of privilege escalation and access bypass, as it allows users with basic authentication credentials to perform actions they should not be authorized to execute within the system.
The technical flaw stems from improper validation of user permissions within the RESTful Web Services module when processing PATCH requests. When a user with authenticated access submits a PATCH request to modify content or system settings, the system fails to adequately verify whether the user possesses the necessary administrative privileges to perform the requested operation. This validation gap occurs because the REST module does not properly enforce the existing access control mechanisms that should normally prevent authenticated users from accessing administrative functions or modifying protected resources. The vulnerability is particularly dangerous because it operates at the application layer, allowing attackers to exploit the flaw without requiring additional authentication factors or elevated privileges beyond basic user access.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it can enable attackers to perform a wide range of malicious activities including content manipulation, user account modification, system configuration changes, and potentially full administrative control over affected Drupal installations. The flaw is especially concerning for organizations that rely on REST APIs for integration purposes, as it can be exploited to compromise not just individual user accounts but entire system functionalities. Attackers can leverage this vulnerability to escalate privileges, modify sensitive data, or create backdoor access points within the system, making it a critical concern for any organization running vulnerable Drupal versions.
Organizations should immediately implement mitigations including upgrading to Drupal 8.2.8 or 8.3.1 versions where this vulnerability has been patched, disabling the RESTful Web Services module if it is not actively required, or implementing additional access controls and monitoring measures. The vulnerability aligns with CWE-285 which addresses improper authorization in software systems, and corresponds to ATT&CK technique T1078 which covers valid accounts and privilege escalation. Security teams should also consider implementing network segmentation, API rate limiting, and comprehensive monitoring of REST endpoints to detect and prevent exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to ensure that all Drupal installations remain protected against similar threats, as this vulnerability demonstrates the importance of maintaining up-to-date security patches and proper access control configurations in web application environments.