CVE-2003-0863 in PHP
Summary
by MITRE
The php_check_safe_mode_include_dir function in fopen_wrappers.c of PHP 4.3.x returns a success value (0) when the safe_mode_include_dir variable is not specified in configuration, which differs from the previous failure value and may allow remote attackers to exploit file include vulnerabilities in PHP applications.
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Analysis
by VulDB Data Team • 12/26/2024
The vulnerability described in CVE-2003-0863 represents a critical security flaw in PHP version 4.3.x that directly impacts the safe mode implementation within the fopen_wrappers.c file. This issue specifically affects the php_check_safe_mode_include_dir function which is responsible for validating directory paths during file inclusion operations. When the safe_mode_include_dir configuration variable is not explicitly set in the PHP configuration, the function incorrectly returns a success value of 0 instead of the expected failure condition, creating a dangerous deviation from the intended security behavior.
The technical flaw stems from the improper handling of uninitialized or unset configuration variables within the safe mode protection mechanism. In properly functioning PHP implementations, when safe_mode_include_dir is not configured, the system should reject file inclusion attempts to prevent potential exploitation. However, this vulnerability causes the system to accept such operations when the configuration parameter is missing, effectively bypassing the intended security controls. The function's return value of 0 indicates success where failure was expected, allowing attackers to manipulate file inclusion paths through the vulnerable code path.
The operational impact of this vulnerability extends beyond simple privilege escalation as it creates a pathway for remote attackers to exploit file include vulnerabilities within PHP applications. Attackers can leverage this flaw to bypass safe mode restrictions that are designed to prevent unauthorized file access and inclusion operations. This weakness specifically targets applications that rely on PHP's safe mode protection mechanisms to prevent directory traversal attacks, remote file inclusion exploits, and local file inclusion vulnerabilities. The vulnerability essentially provides a backdoor mechanism that allows attackers to circumvent the security boundaries established by safe mode, potentially enabling them to include arbitrary files from locations they should not have access to.
From a cybersecurity perspective, this vulnerability aligns with CWE-284, which addresses improper access control in software systems, and represents a classic example of insecure default configuration handling. The flaw demonstrates how configuration parameter validation can be improperly implemented, creating security holes that attackers can exploit. Organizations running PHP 4.3.x applications are particularly at risk since this vulnerability allows for the exploitation of file inclusion attacks that could lead to complete system compromise. The issue also relates to ATT&CK technique T1505.003, which covers web shell deployment through file inclusion vulnerabilities, as attackers can use this flaw to establish persistent access to compromised systems.
Mitigation strategies for this vulnerability require immediate attention and include updating to PHP versions that address this specific flaw, typically PHP 4.3.3 or later releases. Administrators should also implement proper configuration management to ensure that safe_mode_include_dir is explicitly set with appropriate directory restrictions. Additionally, organizations should conduct comprehensive security assessments of their PHP applications to identify potential exploitation vectors and implement proper input validation controls. The recommended approach involves disabling safe mode entirely in favor of more robust security mechanisms and ensuring that all file inclusion operations are properly validated against whitelisted directories to prevent unauthorized access to system resources.