CVE-2005-4424 in PHPKIT
Summary
by MITRE
Directory traversal vulnerability in PHPKIT 1.6.1 R2 and earlier might allow remote authenticated users to execute arbitrary PHP code via a .. (dot dot) in the path parameter and a %00 at the end of the filename, as demonstrated by an avatar filename ending with .png%00.
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Analysis
by VulDB Data Team • 07/07/2021
The directory traversal vulnerability identified in PHPKIT 1.6.1 R2 and earlier versions represents a critical security flaw that enables authenticated remote attackers to execute arbitrary PHP code through carefully crafted input manipulation. This vulnerability resides in the file handling mechanisms of the PHPKIT content management system, specifically within how the application processes path parameters and filename inputs. The flaw manifests when the system fails to properly validate and sanitize user-supplied path data, creating an opportunity for attackers to navigate beyond intended directories and inject malicious code into the system.
The technical exploitation of this vulnerability requires an authenticated user context, which significantly reduces the attack surface compared to fully unauthenticated exploits. Attackers leverage the combination of directory traversal sequences using double dots followed by a null byte termination to manipulate file paths. The specific technique involves appending a .. (dot dot) sequence to navigate up directory levels and concluding with a %00 null byte to terminate the filename string. This particular approach targets the avatar upload functionality where the system processes user-uploaded files with .png extension. The null byte termination effectively bypasses certain input validation checks that might otherwise prevent directory traversal attempts.
The operational impact of this vulnerability extends beyond simple file access violations to encompass complete system compromise. When an authenticated user uploads a specially crafted avatar file ending with .png%00, the vulnerable system processes this input without proper sanitization, allowing the attacker to execute arbitrary PHP code within the web application's execution context. This represents a severe privilege escalation scenario where legitimate users can leverage their authenticated access to perform malicious operations. The vulnerability essentially provides a backdoor for attackers to execute commands on the server, potentially leading to data theft, system infiltration, or complete server takeover.
This vulnerability maps directly to CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal. The specific implementation flaw aligns with ATT&CK technique T1059.007, which covers the use of PHP for executing commands on compromised systems. The attack vector demonstrates how authenticated users can exploit weak input validation mechanisms to achieve code execution, representing a common pattern in web application security vulnerabilities. The combination of path traversal and null byte injection techniques showcases how attackers can circumvent traditional security controls through creative input manipulation.
Mitigation strategies for this vulnerability require immediate patching of the affected PHPKIT versions to address the core path validation flaws. Organizations should implement comprehensive input sanitization measures that properly validate and filter all user-supplied path data, particularly when processing file uploads. The implementation of strict filename validation that rejects special characters including null bytes and directory traversal sequences represents a fundamental defensive measure. Additionally, the system should enforce proper file extension validation and implement upload restrictions that prevent execution of PHP code within user-uploaded directories. Security monitoring should include detection of suspicious file upload patterns and unusual directory traversal attempts to identify potential exploitation attempts. Network segmentation and least privilege access controls can help limit the potential damage from successful exploitation attempts.