CVE-2017-6377 in Drupal
Summary
by MITRE
When adding a private file via the editor in Drupal 8.2.x before 8.2.7, the editor will not correctly check access for the file being attached, resulting in an access bypass.
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Analysis
by VulDB Data Team • 09/09/2020
The vulnerability described in CVE-2017-6377 represents a critical access control flaw within the Drupal content management system that specifically affects versions 8.2.x prior to 8.2.7. This issue manifests when users attempt to attach private files through the rich text editor interface, creating a scenario where the system fails to properly validate user permissions before allowing file attachment operations. The flaw exists in the file access checking mechanism within Drupal's core editor functionality, which is designed to prevent unauthorized access to private content but instead permits bypass of these security controls under specific conditions.
The technical implementation of this vulnerability stems from insufficient input validation and access control enforcement within the file attachment process. When a user attempts to add a private file to content through the editor, the system should verify that the user possesses appropriate permissions to access the file before permitting the attachment. However, the flaw allows malicious or unauthorized users to bypass this critical permission check, potentially enabling them to attach files they should not have access to. This represents a direct violation of the principle of least privilege and demonstrates a failure in the application's authorization mechanisms.
From an operational perspective, this vulnerability poses significant risks to Drupal installations that rely on private file handling for sensitive content management. Attackers could exploit this flaw to gain access to private documents, media files, or other restricted content that should only be accessible to authorized personnel. The impact extends beyond simple unauthorized file access, as it may enable attackers to escalate privileges or gain further access to the system through the attached files. This vulnerability directly relates to CWE-284 which addresses improper access control and aligns with ATT&CK technique T1078 for valid accounts and T1566 for spearphishing with a malicious attachment, as the exploitation could involve tricking users into attaching malicious files.
The mitigation strategy for CVE-2017-6377 requires immediate implementation of the security patch released by Drupal for versions 8.2.7 and later. Organizations should also conduct thorough audits of their file access controls and review user permissions to ensure that no unauthorized access has occurred. Additional defensive measures include implementing network-level access controls, monitoring for unusual file attachment patterns, and ensuring that all Drupal installations are kept current with security updates. The vulnerability highlights the critical importance of proper access control implementation in web applications and demonstrates how seemingly minor flaws in permission checking can result in significant security breaches. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other components of the Drupal ecosystem and prevent exploitation of similar access control bypass vulnerabilities.