CVE-2001-0042 in HTTP Server
Summary
by MITRE
PHP 3.x (PHP3) on Apache 1.3.6 allows remote attackers to read arbitrary files via a modified .. (dot dot) attack containing "%5c" (encoded backslash) sequences.
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Analysis
by VulDB Data Team • 12/10/2024
This vulnerability exists in PHP 3.x versions running on Apache 1.3.6 servers and represents a classic path traversal attack that exploits improper input validation in file handling operations. The flaw occurs when PHP processes file paths that contain encoded backslash sequences, specifically "%5c" which represents a backslash character in URL encoding. Attackers can manipulate file access requests by inserting these encoded sequences into file path parameters, allowing them to traverse the filesystem beyond intended boundaries and access restricted files on the server.
The technical implementation of this vulnerability stems from PHP 3.x's inadequate sanitization of file path inputs during file operations. When the web server processes requests containing "%5c" sequences, the PHP interpreter fails to properly normalize or validate these path components, enabling attackers to bypass directory restrictions. This vulnerability falls under CWE-22 Path Traversal and aligns with ATT&CK technique T1083 File and Directory Discovery, as it allows adversaries to enumerate and access sensitive files that should remain protected. The attack vector specifically leverages the Apache web server's handling of PHP requests combined with PHP 3.x's insufficient input validation mechanisms.
The operational impact of this vulnerability is significant as it allows remote attackers to access arbitrary files on the target system, potentially including configuration files, database credentials, source code, and other sensitive data. Attackers can exploit this weakness to gain unauthorized access to system resources, potentially leading to complete system compromise. The vulnerability affects systems where PHP 3.x is used in conjunction with Apache 1.3.6, representing a critical security risk for any web application that relies on file access functions without proper input validation. The attack can be executed without authentication and requires minimal technical expertise, making it particularly dangerous in production environments.
The primary mitigation strategy involves upgrading to newer versions of PHP where proper input validation and path normalization have been implemented. System administrators should immediately upgrade from PHP 3.x to PHP 4.x or later versions that include enhanced security measures for file path handling. Additionally, implementing proper input validation at the application level, configuring web server restrictions to prevent directory traversal attempts, and applying security patches to Apache 1.3.6 are essential defensive measures. Organizations should also consider implementing web application firewalls and monitoring for suspicious file access patterns. The vulnerability demonstrates the critical importance of proper input validation and the dangers of using outdated software versions in web server environments.