CVE-2015-2087 in Avatar Uploader
Summary
by MITRE
Unrestricted file upload vulnerability in the Avatar Uploader module before 6.x-1.3 for Drupal allows remote authenticated users to execute arbitrary PHP code by uploading a file with a PHP extension, then accessing it via unspecified vectors.
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Analysis
by VulDB Data Team • 04/16/2022
The CVE-2015-2087 vulnerability represents a critical unrestricted file upload flaw within the Avatar Uploader module for Drupal versions prior to 6.x-1.3. This vulnerability resides in the module's handling of user-uploaded files, specifically affecting authenticated users who possess the privilege to upload avatars. The flaw stems from inadequate input validation and sanitization mechanisms that fail to properly verify the content and extension of uploaded files, creating a pathway for malicious code execution. The vulnerability operates under the principle of insufficient validation of file types, a common weakness that directly correlates with CWE-434, which addresses the improper restriction of uploads of executable files.
The technical exploitation of this vulnerability requires an authenticated user to upload a file containing PHP code with a .php extension, typically through the avatar upload interface. Once uploaded, the malicious file becomes accessible via unspecified vectors that allow remote code execution. This attack vector enables adversaries to execute arbitrary commands on the affected Drupal system, potentially leading to complete system compromise. The vulnerability's impact extends beyond simple code execution as it can be leveraged to establish persistent backdoors, exfiltrate sensitive data, or deploy additional malware within the compromised environment. The unspecified vectors for accessing the uploaded files indicate that the vulnerability may be exploitable through multiple pathways, including direct access to the uploaded file location or through misconfigured web server settings.
From an operational perspective, this vulnerability poses significant risks to organizations running vulnerable Drupal installations, particularly those with user registration enabled and administrative privileges granted to authenticated users. The attack surface expands when considering that many organizations maintain user accounts for various purposes including content management, forum participation, or community engagement. The fact that this vulnerability affects authenticated users means that attackers can exploit it through legitimate user accounts, making detection more challenging and potentially allowing for prolonged undetected access. The vulnerability aligns with several ATT&CK techniques including T1059 for command and script injection, T1078 for valid accounts, and T1505 for server-side injection, demonstrating how a single flaw can enable multiple attack phases.
Organizations should prioritize immediate remediation by upgrading to Drupal 6.x-1.3 or later versions of the Avatar Uploader module, as this addresses the core validation issues that enable the vulnerability. Additionally, implementing strict file type validation and sanitization measures can provide defense-in-depth protection. Web application firewalls and intrusion detection systems should be configured to monitor for suspicious file upload activities and PHP file access patterns. The vulnerability highlights the importance of secure coding practices and proper input validation, particularly when handling user-supplied content. Organizations should also consider implementing file extension whitelisting, enforcing strict file content verification, and ensuring proper file permissions and access controls. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other modules and components of the Drupal platform, as this vulnerability demonstrates how seemingly minor flaws can lead to severe security consequences and aligns with the broader category of insecure file handling practices described in CWE-434 and CWE-22.