CVE-2015-3013 in ownCloud
Summary
by MITRE
ownCloud Server before 5.0.19, 6.x before 6.0.7, and 7.x before 7.0.5 allows remote authenticated users to bypass the file blacklist and upload arbitrary files via a file path with UTF-8 encoding, as demonstrated by uploading a .htaccess file.
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Analysis
by VulDB Data Team • 04/01/2025
The vulnerability CVE-2015-3013 represents a critical security flaw in ownCloud Server versions prior to specific patch releases, exposing organizations to significant risks through improper file validation mechanisms. This issue affects multiple version streams including 5.x before 5.0.19, 6.x before 6.0.7, and 7.x before 7.0.5, indicating a widespread problem within the software's file handling architecture. The vulnerability specifically targets the file blacklist implementation, which is designed to prevent users from uploading potentially malicious files that could compromise system security.
The technical exploitation of this vulnerability relies on UTF-8 encoding manipulation within file paths, allowing authenticated users to bypass the intended security controls. When users upload files with UTF-8 encoded paths, the system fails to properly validate the file extensions and content, enabling attackers to circumvent the blacklist restrictions. This particular weakness demonstrates a classic input validation flaw that has been categorized under CWE-20 as "Improper Input Validation," where the application fails to properly validate or sanitize user-supplied data before processing it.
The operational impact of this vulnerability extends beyond simple file uploads, as demonstrated by the specific example of uploading .htaccess files. This capability allows attackers to potentially modify server configuration files, leading to various security consequences including but not limited to web server misconfiguration, potential code execution, or unauthorized access to sensitive system resources. The ability to upload .htaccess files specifically enables attackers to modify Apache server behavior, potentially creating backdoors or altering security settings that could persist across system restarts.
From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript" and T1078.004 for "Valid Accounts: Cloud Accounts" as it leverages authenticated user access to perform unauthorized actions. The vulnerability's exploitation requires only authenticated access, making it particularly dangerous as it can be leveraged by insiders or compromised accounts. Organizations using affected versions of ownCloud face significant risks including data exfiltration, system compromise, and potential lateral movement within their network infrastructure.
Mitigation strategies for CVE-2015-3013 should prioritize immediate patching of all affected ownCloud Server installations to the recommended versions that contain proper UTF-8 encoding handling and file validation. Additionally, organizations should implement additional security controls such as enhanced file type validation, regular security auditing of uploaded files, and monitoring for suspicious file upload activities. Network segmentation and principle of least privilege access controls can help limit the potential impact if exploitation occurs. The vulnerability also highlights the importance of proper internationalization handling in security-critical applications, as UTF-8 encoding issues can create unexpected security gaps when not properly addressed in input validation routines.