CVE-2017-6926 in Drupal
Summary
by MITRE
In Drupal versions 8.4.x versions before 8.4.5 users with permission to post comments are able to view content and comments they do not have access to, and are also able to add comments to this content. This vulnerability is mitigated by the fact that the comment system must be enabled and the attacker must have permission to post comments.
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Analysis
by VulDB Data Team • 02/10/2023
The vulnerability identified as CVE-2017-6926 represents a significant access control flaw within the Drupal content management system affecting versions 8.4.x prior to 8.4.5. This issue resides in the core comment system implementation where users possessing the specific permission to post comments can exploit a logic flaw that allows them to bypass normal content access restrictions. The vulnerability operates at the application level and specifically targets the authorization mechanisms that should prevent unauthorized access to content and comment functionality. The flaw essentially allows authenticated users to perform actions they should not be permitted to execute based on their assigned permissions.
The technical nature of this vulnerability stems from improper validation of access controls within the comment submission process. When users attempt to post comments, the system fails to adequately verify whether the user has proper authorization to access the target content and its associated comments. This creates a scenario where users can view restricted content simply by accessing the comment section of that content, and subsequently add comments to content they would normally be denied access to. The flaw manifests as a failure in the permission checking logic that should occur before allowing comment operations to proceed. This type of vulnerability falls under the CWE-284 category of Improper Access Control, which specifically addresses insufficient access control mechanisms in software applications. The vulnerability represents a classic case of privilege escalation through improper authorization checks.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates opportunities for unauthorized content manipulation and potential data exposure. Attackers with comment posting permissions can effectively gain access to content that should be restricted to specific user roles or groups, potentially exposing sensitive information or internal communications. The ability to add comments to restricted content also provides a vector for potential data injection or manipulation attacks. This vulnerability particularly affects organizations that rely on Drupal for content management and have users with comment privileges, as it undermines the fundamental security model of access control and content protection. The impact is exacerbated when organizations have complex user permission structures or when content contains confidential information that should only be accessible to specific user groups.
Mitigation strategies for CVE-2017-6926 primarily focus on immediate software updates to versions 8.4.5 or later where the vulnerability has been patched. Organizations should also implement additional security measures including regular permission reviews to ensure that comment posting privileges are appropriately restricted to trusted users only. The patch addresses the core authorization logic flaw by implementing proper access control checks before allowing comment operations to proceed. Security teams should conduct comprehensive audits of user permissions and content access controls to identify any potential exploitation of this vulnerability. Additionally, organizations should consider implementing network-level monitoring to detect unusual comment posting patterns that might indicate exploitation attempts. The vulnerability demonstrates the critical importance of proper access control implementation and the need for thorough security testing of core application features. Organizations should also review their overall security posture and ensure that all Drupal installations are kept up to date with the latest security patches to prevent similar vulnerabilities from being exploited.