CVE-2012-5609 in ownCloud
Summary
by MITRE
Incomplete blacklist vulnerability in lib/migrate.php in ownCloud before 4.5.2 allows remote authenticated users to execute arbitrary PHP code by uploading a crafted mount.php file in a ZIP file.
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Analysis
by VulDB Data Team • 03/31/2025
The vulnerability described in CVE-2012-5609 represents a critical security flaw in the ownCloud file sharing platform that affected versions prior to 4.5.2. This issue stems from an incomplete blacklist implementation in the lib/migrate.php component, which governs the handling of file uploads and migrations within the system. The vulnerability specifically targets the file type validation mechanism that is supposed to prevent the execution of potentially malicious PHP code through file uploads. The flaw allows authenticated attackers to bypass security restrictions by crafting malicious ZIP archives containing specially named files that evade the detection system.
The technical exploitation of this vulnerability occurs through a carefully constructed ZIP archive that includes a mount.php file with specific naming conventions designed to circumvent the existing blacklist validation. When the ownCloud system processes this archive, it fails to properly validate the file extension or content of the mount.php file, allowing it to be executed as PHP code on the server. This represents a classic incomplete blacklist vulnerability pattern where the system relies on a limited set of file extensions to block malicious uploads, but fails to account for all possible variations or encoding methods that attackers can employ. The vulnerability directly maps to CWE-20, which describes improper input validation, and more specifically to CWE-434, which addresses unrestricted file upload.
The operational impact of this vulnerability is severe as it grants authenticated remote attackers the ability to execute arbitrary PHP code on the affected ownCloud server. This privilege escalation allows attackers to potentially gain full control over the file sharing platform, access sensitive user data, modify or delete files, and establish persistent backdoors. The authentication requirement does not significantly reduce the risk as the vulnerability can be exploited by any user with valid credentials, which could include compromised accounts or malicious insiders. The attack vector leverages the legitimate file upload functionality, making it difficult to detect through traditional network monitoring systems. This vulnerability aligns with ATT&CK technique T1190, which describes exploiting vulnerabilities in applications to execute code, and T1078, which covers legitimate credentials usage for persistence.
Mitigation strategies for this vulnerability involve implementing proper input validation and whitelisting mechanisms rather than relying on blacklists. The recommended approach includes updating to ownCloud version 4.5.2 or later, which contains the necessary patches to address the incomplete blacklist implementation. Organizations should also implement strict file type validation that checks not only file extensions but also file content signatures to prevent PHP code execution. Additional security measures include restricting file upload capabilities to specific user roles, implementing proper file access controls, and conducting regular security audits of file handling components. The vulnerability demonstrates the importance of defense in depth and the need for robust validation mechanisms that consider multiple attack vectors rather than relying solely on simple extension-based filtering.