CVE-2007-5156 in FCKeditor
Summary
by MITRE
Incomplete blacklist vulnerability in editor/filemanager/upload/php/upload.php in FCKeditor, as used in SiteX CMS 0.7.3.beta, La-Nai CMS, Syntax CMS, Cardinal Cms, and probably other products, allows remote attackers to upload and execute arbitrary PHP code via a file whose name contains ".php." and has an unknown extension, which is recognized as a .php file by the Apache HTTP server, a different vulnerability than CVE-2006-0658 and CVE-2006-2529.
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Analysis
by VulDB Data Team • 10/22/2024
The vulnerability described in CVE-2007-5156 represents a critical security flaw in FCKeditor's file upload functionality that affects multiple content management systems including SiteX CMS 0.7.3.beta and La-Nai CMS. This issue stems from an incomplete blacklist implementation in the upload.php script located at editor/filemanager/upload/php/upload.php, creating a dangerous pathway for remote code execution attacks. The flaw specifically exploits how the system handles file extensions and name validation, allowing malicious actors to bypass security measures through cleverly crafted file naming techniques.
The technical implementation of this vulnerability relies on a sophisticated bypass mechanism that leverages the Apache HTTP server's file processing behavior. Attackers can craft filenames containing ".php." followed by another extension such as ".php.jpg" or ".php.gif" which the vulnerable system incorrectly accepts and processes. While the upload mechanism may appear to validate file extensions, the underlying flaw occurs when Apache interprets these files based on their final extension rather than the initial validation logic. This creates a mismatch between the application's security controls and the web server's actual file handling behavior, which is a classic example of insecure input validation and improper security boundary enforcement.
The operational impact of this vulnerability extends far beyond simple file upload capabilities, as it provides attackers with the ability to execute arbitrary PHP code on the target server. This represents a severe privilege escalation opportunity that can lead to complete system compromise, data exfiltration, and persistent backdoor access. The vulnerability affects multiple CMS platforms, amplifying its potential impact across various web applications that rely on FCKeditor for content management. Organizations using these affected systems face significant risk of unauthorized code execution, which can result in service disruption, data loss, and compliance violations. The attack vector requires minimal sophistication while offering maximum impact, making it particularly dangerous in environments where multiple vulnerable applications exist.
The vulnerability aligns with CWE-434, which describes insecure file upload scenarios where applications accept files without proper validation of their content or extension. It also relates to ATT&CK technique T1190, which covers exploiting vulnerabilities in web applications to achieve code execution. Organizations should implement comprehensive mitigations including strict file extension validation, content type checking, and proper file handling mechanisms that prevent the execution of uploaded files. Additionally, the use of secure file upload libraries and frameworks that properly validate file contents rather than relying solely on extension filtering is essential. Network segmentation and monitoring for suspicious file upload activities should also be implemented to detect potential exploitation attempts. The vulnerability demonstrates the critical importance of understanding how different system components interact and the necessity of defense-in-depth strategies that protect against multiple attack vectors.