CVE-2007-5596 in Drupal
Summary
by MITRE
The core Upload module in Drupal 4.7.x before 4.7.8 and 5.x before 5.3 places the .html extension on a whitelist, which allows remote attackers to conduct cross-site scripting (XSS) attacks by uploading .html files.
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Analysis
by VulDB Data Team • 07/29/2019
The vulnerability identified as CVE-2007-5596 represents a critical cross-site scripting flaw in Drupal content management systems that affected versions prior to 4.7.8 and 5.3. This security weakness resides within the core Upload module and demonstrates a significant oversight in file extension validation mechanisms. The flaw specifically allows remote attackers to execute malicious scripts in the context of a victim's browser by exploiting the overly permissive file extension whitelist that includes the .html extension. This vulnerability directly impacts the integrity and security of web applications built on Drupal platforms, particularly those that allow user uploads without proper sanitization measures.
The technical implementation of this vulnerability stems from inadequate input validation within the file upload processing pipeline. When Drupal processes uploaded files through its core Upload module, it maintains a whitelist of acceptable file extensions to prevent the upload of potentially malicious file types such as .php, .asp, or .jsp that could execute server-side code. However, the developers included .html in this whitelist without considering that HTML files can contain malicious javascript code that executes when viewed in a browser. This design decision creates a pathway for attackers to upload HTML files containing embedded javascript payloads that can hijack user sessions, steal cookies, or redirect users to malicious sites. The vulnerability operates under CWE-20, which classifies it as an improper input validation issue, and aligns with ATT&CK technique T1566 for initial access through malicious file uploads.
The operational impact of this vulnerability extends beyond simple XSS attacks, as it can enable more sophisticated exploitation patterns that compromise user sessions and potentially lead to full system compromise. Attackers can craft HTML files containing malicious javascript that leverages the victim's authenticated session to perform actions on their behalf, including modifying content, accessing restricted areas, or stealing sensitive information. The vulnerability is particularly dangerous in multi-user environments where administrators or editors might view uploaded HTML files, as it can facilitate privilege escalation attacks. Additionally, the flaw can be combined with other techniques to create persistent threats that remain active until the malicious files are removed from the system, making it a significant concern for web applications handling user-generated content.
Organizations should implement immediate mitigations including upgrading to Drupal versions 4.7.8 or 5.3 and later, which address this vulnerability through enhanced file extension validation. Security measures should also include implementing additional upload restrictions such as removing .html from the allowed file extensions, enforcing strict file type validation at both client and server levels, and implementing content security policies to prevent script execution in uploaded files. Network-based solutions like web application firewalls can provide additional protection layers, while regular security audits should verify that upload mechanisms properly validate file content rather than relying solely on extension checks. The vulnerability serves as a reminder of the critical importance of proper input validation and the principle of least privilege in web application security, particularly when dealing with user-uploaded content that can be executed in the context of other users' browsers.