CVE-2007-0205 in Alex Guestbook
Summary
by MITRE
Directory traversal vulnerability in admin/skins.php for @lex Guestbook 4.0.2 and earlier allows remote attackers to create files in arbitrary directories via ".." sequences in the (1) aj_skin and (2) skin_edit parameters. NOTE: this can be leveraged for file inclusion by creating a skin file in the lang directory, then referencing that file via the lang parameter to index.php, which passes a sanity check in livre_include.php.
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Analysis
by VulDB Data Team • 08/17/2024
The vulnerability described in CVE-2007-0205 represents a critical directory traversal flaw within the @lex Guestbook 4.0.2 and earlier versions, specifically affecting the admin/skins.php component. This security weakness stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied data containing directory traversal sequences. The vulnerability manifests when remote attackers exploit the aj_skin and skin_edit parameters through the use of ".." sequences, which are standard directory traversal indicators that allow access to parent directories in file systems. The flaw operates at the application level and demonstrates poor input filtering practices that directly enable attackers to manipulate file system paths beyond intended boundaries.
The technical execution of this vulnerability involves attackers crafting malicious input strings containing directory traversal sequences within the aj_skin and skin_edit parameters. When the application processes these parameters without proper validation, it permits the creation of files in arbitrary directories throughout the file system. This capability extends beyond simple file creation to include potential file inclusion attacks, as demonstrated by the ability to place malicious skin files in the lang directory and subsequently reference them through the lang parameter in index.php. The exploitation chain leverages the livre_include.php component which performs only basic sanity checks, failing to prevent the inclusion of maliciously crafted files. This vulnerability falls under the CWE-22 category of Improper Limitation of a Pathname to a Restricted Directory, which is a well-documented weakness in web application security.
The operational impact of this vulnerability is substantial as it provides attackers with unauthorized file system access and potential code execution capabilities. Remote attackers can leverage this flaw to upload malicious files, create backdoors, or modify existing application components, potentially leading to complete system compromise. The vulnerability's exploitability is enhanced by its remote nature, meaning attackers do not require physical access or local privileges to exploit the flaw. The chained nature of the attack, combining directory traversal with file inclusion, significantly increases the attack surface and potential damage. This vulnerability represents a classic example of how insufficient input validation can lead to privilege escalation and arbitrary code execution in web applications. The flaw also aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1505.003 for Server Software Component, as it enables attackers to manipulate server components through file system manipulation.
Mitigation strategies for this vulnerability must address both the immediate directory traversal issue and the broader input validation weaknesses that enable the exploit chain. Organizations should implement strict input validation and sanitization for all user-supplied parameters, particularly those related to file paths and directory operations. The application should enforce absolute path restrictions and reject any input containing directory traversal sequences. Additionally, proper access controls and file system permissions should be implemented to limit the application's ability to create files in sensitive directories. The fix should include comprehensive parameter validation that ensures all file operations occur within designated safe directories, preventing arbitrary path manipulation. Regular security audits and input validation testing should be conducted to identify and remediate similar vulnerabilities across the application stack. This vulnerability highlights the importance of secure coding practices and proper input validation as fundamental defenses against directory traversal attacks.