CVE-2012-5318 in Kish Guest Posting plugin
Summary
by MITRE
Unrestricted file upload vulnerability in uploadify/scripts/uploadify.php in the Kish Guest Posting plugin 1.2 for WordPress allows remote attackers to execute arbitrary code by uploading a file with a double extension, then accessing it via a direct request to the file in the directory specified by the folder parameter. NOTE: this vulnerability exists because of an incomplete fix for CVE-2012-1125.
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Analysis
by VulDB Data Team • 06/14/2025
The CVE-2012-5318 vulnerability represents a critical security flaw in the Kish Guest Posting plugin version 1.2 for WordPress systems, specifically within the uploadify/scripts/uploadify.php component. This vulnerability constitutes a file upload restriction bypass that enables remote attackers to execute arbitrary code on affected systems. The flaw arises from inadequate input validation and sanitization mechanisms that fail to properly handle file extensions, particularly those with double extensions. The vulnerability is particularly concerning because it builds upon and fails to adequately address a previous security issue documented in CVE-2012-1125, indicating a pattern of incomplete security remediation in the plugin's codebase. The security implications extend beyond simple privilege escalation as they allow for complete system compromise through malicious file execution.
The technical exploitation of this vulnerability occurs through a specific attack vector involving double extension file uploads. Attackers can upload files with extensions such as .php.jpg or .jpg.php where the server processes the file based on the latter extension while appearing to be a legitimate image file. The uploadify.php script accepts user-supplied file uploads without proper validation of the file content or extension handling, allowing attackers to bypass the intended security measures. The vulnerability is further amplified by the fact that the folder parameter in the upload functionality is not properly secured, enabling attackers to specify arbitrary directory paths for file placement. This combination of factors creates a path traversal and code execution scenario where malicious files can be placed in web-accessible directories and subsequently executed by the web server. The vulnerability directly maps to CWE-434 which describes insecure file upload scenarios, and aligns with ATT&CK technique T1190 for exploiting vulnerabilities in web applications.
The operational impact of this vulnerability extends far beyond simple data theft or modification, as it provides attackers with complete system compromise capabilities. Once a malicious file is successfully uploaded, attackers can execute arbitrary code with the privileges of the web server process, potentially leading to full system takeover, data exfiltration, or establishment of persistent backdoors. The vulnerability affects WordPress installations where the Kish Guest Posting plugin is active, making it particularly dangerous for websites that rely on guest posting functionality or similar user upload features. The risk is compounded by the fact that this vulnerability is part of a broader class of file upload flaws that are commonly targeted in automated exploitation campaigns, making affected systems prime targets for botnet recruitment or as stepping stones for further network penetration. The incomplete fix for the previous CVE-2012-1125 vulnerability demonstrates poor security hygiene and suggests that the plugin developers may not have fully understood or addressed the underlying architectural flaws in their file handling implementation.
Mitigation strategies for CVE-2012-5318 should begin with immediate plugin removal or complete update to a patched version if available. Organizations should implement strict file type validation at both the application and web server levels, ensuring that only expected file types are accepted for upload and that file content is verified against its declared extension. The recommended approach includes implementing Content-Type validation, file signature checking, and restricting upload directories to non-web-accessible locations. Network-level defenses such as web application firewalls can help detect and block suspicious upload patterns, while proper access controls and least privilege principles should be enforced to limit the impact of potential exploitation. System administrators should conduct thorough security audits of all installed WordPress plugins to identify similar vulnerabilities and ensure that all security patches are applied promptly. The vulnerability also underscores the importance of proper input validation and the need for comprehensive security testing of web applications, particularly those handling user uploads. Regular security monitoring and vulnerability scanning should be implemented to detect similar issues in other components of the web application stack, as the presence of one such vulnerability often indicates broader security weaknesses in the application architecture.