CVE-2015-6660 in Drupal
Summary
by MITRE
The Form API in Drupal 6.x before 6.37 and 7.x before 7.39 does not properly validate the form token, which allows remote attackers to conduct CSRF attacks that upload files in a different user's account via vectors related to "file upload value callbacks."
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Analysis
by VulDB Data Team • 06/13/2022
The vulnerability identified as CVE-2015-6660 represents a critical cross-site request forgery weakness within Drupal's Form API implementation affecting versions prior to 6.37 and 7.39. This flaw specifically targets the form token validation mechanism that should prevent unauthorized modifications to forms submitted by users. The issue enables attackers to exploit the lack of proper token verification during file upload operations, creating a pathway for malicious actors to execute unauthorized file uploads on behalf of other users.
The technical flaw resides in the insufficient validation of form tokens within Drupal's Form API, which is a fundamental security control designed to ensure that form submissions originate from legitimate sources and have not been tampered with during transmission. When the system fails to properly validate these tokens, it allows attackers to craft malicious requests that appear to be legitimate form submissions from authenticated users. The vulnerability specifically manifests during file upload operations where value callbacks are processed, creating an attack surface that bypasses normal user authentication and authorization checks.
This vulnerability enables remote attackers to conduct sophisticated CSRF attacks that can result in unauthorized file uploads into different user accounts, potentially leading to privilege escalation, data compromise, or system infiltration. The impact extends beyond simple file manipulation as these uploads could contain malicious code that could be executed within the web application context, potentially allowing attackers to gain deeper access to the system. The attack vector leverages the trust relationship between the web application and legitimate users, exploiting the assumption that form submissions with valid tokens are safe to process.
The operational impact of this vulnerability is significant as it undermines the core security model of Drupal applications that rely on proper authentication and authorization mechanisms. Organizations running affected versions of Drupal face potential exposure to unauthorized data manipulation, privilege escalation, and possible complete system compromise. The vulnerability affects not just individual users but entire application ecosystems where multiple users interact with file upload functionalities, creating widespread potential for exploitation.
Security mitigations for this vulnerability include immediate upgrade to Drupal versions 6.37 or 7.39 and later, which contain the necessary patches to properly validate form tokens during file upload operations. Organizations should also implement additional security controls such as input validation, proper session management, and monitoring for unusual file upload patterns. The vulnerability aligns with CWE-352, which describes Cross-Site Request Forgery, and maps to ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting, highlighting the multi-layered nature of the threat. Additionally, organizations should review their form validation configurations and implement proper token regeneration mechanisms to prevent similar vulnerabilities in other components of their web applications.