CVE-2007-3163 in FCKeditor
Summary
by MITRE
Incomplete blacklist vulnerability in the filemanager in Frederico Caldeira Knabben FCKeditor 2.4.2 allows remote attackers to upload arbitrary .php files via an alternate data stream syntax, as demonstrated by .php::$DATA filenames, a related issue to CVE-2006-0658.
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Analysis
by VulDB Data Team • 08/11/2019
The vulnerability identified as CVE-2007-3163 represents a critical security flaw in the FCKeditor 2.4.2 file management component that stems from an incomplete blacklist implementation. This weakness specifically affects the file upload validation mechanism within the editor's filemanager module, creating a pathway for remote attackers to bypass security controls and execute malicious code on vulnerable systems. The vulnerability operates through a sophisticated technique that exploits the Windows file system's alternate data streams feature, which allows multiple data streams to coexist within a single file.
The technical implementation of this vulnerability relies on the manipulation of file naming conventions to circumvent traditional file extension filtering mechanisms. Attackers can exploit this by creating files with names that include the alternate data stream syntax .php::$DATA, which allows them to upload PHP scripts that appear to be legitimate files while maintaining their executable capabilities. This technique demonstrates a fundamental flaw in the validation logic where the system fails to properly sanitize file names against all possible representations of the same file, particularly when dealing with operating system-specific features like Windows alternate data streams.
The operational impact of this vulnerability extends beyond simple unauthorized file uploads, as it enables remote code execution capabilities that can lead to complete system compromise. When successful, attackers can upload malicious PHP payloads that execute with the privileges of the web server process, potentially allowing for data theft, system infiltration, and further lateral movement within network environments. This vulnerability directly maps to CWE-434, which describes insecure file upload vulnerabilities where applications accept files without proper validation of their content or naming conventions. The attack vector specifically aligns with ATT&CK technique T1190, which involves exploiting vulnerabilities in web applications to execute arbitrary code.
The security implications of this vulnerability are particularly severe because it demonstrates how seemingly minor implementation flaws in input validation can create significant attack surfaces. The incomplete blacklist approach fails to account for all possible ways that file names can be represented, particularly when leveraging operating system-specific features that are not commonly considered in standard security validation processes. This type of vulnerability highlights the importance of defense-in-depth strategies and the necessity of implementing proper input sanitization that considers all potential representations of malicious input rather than relying on simple pattern matching approaches. Organizations using FCKeditor 2.4.2 were particularly vulnerable as this flaw allowed attackers to effectively bypass security controls that should have prevented the execution of potentially harmful code through file upload mechanisms.