CVE-2004-1392 in PHP
Summary
by MITRE
PHP 4.0 with cURL functions allows remote attackers to bypass the open_basedir setting and read arbitrary files via a file: URL argument to the curl_init function.
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Analysis
by VulDB Data Team • 02/01/2025
The vulnerability described in CVE-2004-1392 represents a critical security flaw in PHP 4.0's implementation of cURL functions that directly undermines fundamental web server security mechanisms. This issue specifically targets the open_basedir directive, which serves as a crucial restriction mechanism in PHP environments designed to limit file access to specific directories and prevent unauthorized file system traversal attacks. The vulnerability allows remote attackers to circumvent these protective measures through the manipulation of file: URL arguments passed to the curl_init function, effectively enabling arbitrary file reading capabilities that should otherwise be restricted.
The technical exploitation of this vulnerability occurs through the improper handling of file protocol URLs within the cURL extension of PHP 4.0. When a malicious user provides a file: URL as an argument to curl_init, the underlying cURL library fails to properly validate or sanitize the URL before attempting to access the specified resource. This flaw exists because the PHP cURL implementation does not adequately enforce the open_basedir restrictions when processing file:// URLs, allowing attackers to bypass the configured directory boundaries. The vulnerability specifically affects PHP versions prior to 4.3.10 and 5.0.4, where the cURL extension lacked proper validation of file protocol URLs against the open_basedir configuration settings.
The operational impact of this vulnerability is severe and multifaceted, as it enables attackers to access sensitive files that should be protected by the open_basedir directive. This includes configuration files, database credentials, user data, and potentially system files that contain critical information. Attackers can leverage this vulnerability to extract database connection strings, application secrets, user authentication details, and other confidential information stored on the server. The ability to read arbitrary files through a remote attack vector transforms what should be a controlled access environment into a potential data breach scenario, where the attacker can systematically explore the file system and extract valuable information without requiring local system access or elevated privileges.
This vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, and specifically demonstrates how file protocol handling can bypass directory restrictions. From an ATT&CK framework perspective, this vulnerability maps to T1083 (File and Directory Discovery) and T1566 (Phishing with Malicious Attachment) as attackers can use this technique to discover and extract sensitive files from compromised systems. The vulnerability also relates to T1595 (Active Scanning] as it enables reconnaissance activities that can reveal the structure and contents of target systems. Organizations affected by this vulnerability face significant risk of data exposure, potential system compromise, and compliance violations, particularly in environments where sensitive data processing occurs.
The primary mitigation strategy involves upgrading PHP installations to versions that properly address this vulnerability, specifically PHP 4.3.10 or later for PHP 4.0 installations, and PHP 5.0.4 or later for PHP 5.0 installations. System administrators should also implement additional security controls such as disabling unnecessary cURL functions when possible, configuring strict file access controls, and monitoring for suspicious file access patterns. Network-level protections including web application firewalls and intrusion detection systems can help detect and block exploitation attempts. Organizations should also conduct thorough security assessments to identify all systems running vulnerable PHP versions and ensure proper patch management processes are in place to prevent similar vulnerabilities from being introduced in the future. The vulnerability highlights the importance of proper input validation and the need for security-conscious development practices when implementing network communication libraries and file access mechanisms.