CVE-2007-3378 in PHP
Summary
by MITRE
The (1) session_save_path, (2) ini_set, and (3) error_log functions in PHP 4.4.7 and earlier, and PHP 5 5.2.3 and earlier, when invoked from a .htaccess file, allow remote attackers to bypass safe_mode and open_basedir restrictions and possibly execute arbitrary commands, as demonstrated using (a) php_value, (b) php_flag, and (c) directives in .htaccess.
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Analysis
by VulDB Data Team • 03/16/2021
The vulnerability described in CVE-2007-3378 represents a critical security flaw in PHP versions prior to 4.4.7 and 5.2.3 that fundamentally undermines the security model of web applications. This issue arises from the improper handling of configuration directives when PHP processes .htaccess files, creating a pathway for remote attackers to circumvent essential security restrictions. The flaw specifically affects three core PHP functions: session_save_path, ini_set, and error_log, which when invoked through .htaccess directives can be exploited to bypass critical safe_mode and open_basedir restrictions. These restrictions are fundamental to PHP's security architecture, designed to limit file system access and prevent unauthorized code execution within web server environments.
The technical implementation of this vulnerability stems from PHP's handling of configuration directives within the .htaccess file context, which operates outside the normal execution boundaries of PHP scripts. When attackers use php_value, php_flag, or similar directives in .htaccess files, they can manipulate the runtime environment in ways that were not intended by the PHP developers. This misconfiguration allows for the modification of critical PHP settings that control file access permissions and execution contexts, effectively creating a backdoor that bypasses the normal security checks. The vulnerability operates at the intersection of web server configuration and PHP's runtime behavior, exploiting the trust placed in .htaccess files as legitimate configuration mechanisms while simultaneously undermining the security boundaries that separate different execution contexts.
The operational impact of this vulnerability is severe and far-reaching, as it enables attackers to execute arbitrary commands on vulnerable systems with elevated privileges. This capability allows for complete system compromise, data exfiltration, and persistent access to affected environments. The ability to bypass safe_mode restrictions means that attackers can access files and directories that should normally be restricted, while open_basedir bypasses prevent them from being contained within specific directories. This vulnerability directly relates to CWE-276, which addresses improper privileges and access control, and aligns with ATT&CK technique T1548.001 for privilege escalation through configuration modification. The exploitation process typically involves crafting malicious .htaccess files that contain PHP configuration directives, which when processed by the web server, modify PHP's runtime behavior to enable unauthorized access and command execution.
Mitigation strategies for CVE-2007-3378 must address both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities. The primary solution involves upgrading to PHP versions 4.4.7 or later and 5.2.3 or later, where the vulnerability has been patched. Organizations should also implement strict .htaccess file permissions and audit all configuration directives that might affect PHP behavior. Security measures should include disabling the ability to modify PHP settings through .htaccess files when possible, implementing proper input validation for configuration parameters, and establishing monitoring for unusual .htaccess file modifications. The vulnerability demonstrates the critical importance of understanding how web server configuration interacts with application runtime environments and highlights the necessity of maintaining up-to-date software versions to prevent exploitation of known security flaws. Additionally, organizations should consider implementing Web Application Firewalls and runtime application self-protection mechanisms to detect and prevent exploitation attempts targeting similar configuration-based vulnerabilities.