CVE-2013-1850 in ownCloud
Summary
by MITRE
Multiple incomplete blacklist vulnerabilities in (1) import.php and (2) ajax/uploadimport.php in apps/contacts/ in ownCloud before 4.0.13 and 4.5.x before 4.5.8 allow remote authenticated users to execute arbitrary PHP code by uploading a .htaccess file.
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Analysis
by VulDB Data Team • 03/31/2025
The vulnerability CVE-2013-1850 represents a critical security flaw in the ownCloud file sharing platform that affects versions prior to 4.0.13 and 4.5.x before 4.5.8. This issue stems from inadequate input validation and file handling mechanisms within the contacts application module, specifically in two key files: import.php and ajax/uploadimport.php. The vulnerability classifies under CWE-20, which denotes improper input validation, and falls into the broader category of insecure file upload vulnerabilities that have been extensively documented in security frameworks including the OWASP Top Ten. The flaw allows authenticated attackers to bypass security restrictions through the manipulation of file upload processes, creating a pathway for remote code execution.
The technical implementation of this vulnerability exploits the incomplete blacklist approach used by ownCloud to filter uploaded files. When users upload files through the contacts application, the system should validate file types and prevent the upload of potentially dangerous files such as .htaccess files that could be used to modify server configurations. However, the blacklist mechanism was insufficiently restrictive, allowing attackers to upload .htaccess files that would be processed by the web server and potentially execute arbitrary PHP code. This occurs because .htaccess files can contain directives that modify server behavior, and when processed by the vulnerable ownCloud application, these files could be interpreted as executable code rather than configuration data.
The operational impact of this vulnerability is severe and multifaceted. Remote authenticated users who can access the ownCloud contacts application can leverage this flaw to execute arbitrary code on the server hosting the application, potentially leading to complete system compromise. This vulnerability directly maps to ATT&CK technique T1059.007 for execution through web shells and T1078 for valid accounts to maintain persistent access. The attack vector requires only authentication credentials to the ownCloud system, making it particularly dangerous in environments where user access is not strictly controlled. Successful exploitation could result in data theft, system manipulation, service disruption, and potential lateral movement within network infrastructure.
Mitigation strategies for CVE-2013-1850 should prioritize immediate patching of affected ownCloud versions to 4.0.13 or 4.5.8 respectively, as these releases contain the necessary fixes for the file upload validation mechanisms. Organizations should implement additional defensive measures including stricter file type validation, mandatory file extension whitelisting, and comprehensive file content analysis before processing uploads. The solution should also incorporate proper input sanitization and ensure that uploaded files are stored in non-executable directories. Security monitoring should be enhanced to detect suspicious file upload activities, and access controls should be reviewed to minimize the attack surface. This vulnerability demonstrates the critical importance of proper input validation and the dangers of relying solely on blacklist-based security approaches, reinforcing principles from the NIST Cybersecurity Framework and ISO 27001 standards for secure application development.