CVE-2006-7243 in PHP
Prediction
by VulDB Data Team • 06/14/2025
A vulnerability was detected in PHP up to 5.3.3. Affected by this vulnerability is the function file_exists of the component File Extension Handler. Performing a manipulation results in improper access controls. It is possible to initiate the attack remotely. Upgrading to version 5.3.4 addresses this issue. It is suggested to upgrade the affected component.
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Analysis
by VulDB Data Team • 06/14/2025
This vulnerability in PHP versions prior to 5.3.4 represents a critical security flaw that exploits improper handling of null bytes in file pathnames. The issue stems from PHP's failure to properly sanitize input containing null characters, which can be used to manipulate file access controls and bypass security restrictions. The vulnerability specifically affects the file_exists function and similar file operations that process pathnames containing null terminators. When a null byte is embedded within a filename, PHP's internal processing can truncate the string at that point, potentially allowing attackers to manipulate the file extension and bypass intended access controls. This behavior creates a significant attack surface where malicious actors can craft filenames that appear to have safe extensions like .jpg while actually containing embedded null bytes that alter the effective file processing.
The technical implementation of this vulnerability leverages the way PHP handles string termination and file path parsing. When PHP encounters a null byte within a pathname, it treats this character as a string terminator rather than part of the filename, effectively truncating the path at that point. This creates a scenario where a filename like .php.jpg might be interpreted as .php, allowing PHP to execute the file as a PHP script despite the apparent image extension. The vulnerability operates at the intersection of multiple security concerns including input validation, file access control, and string processing. According to CWE-170, this represents a flaw in handling of null terminators, which can lead to various security implications including information disclosure and code execution. The vulnerability demonstrates how seemingly minor implementation details in string processing can create significant security weaknesses that affect core system functionality.
The operational impact of this vulnerability extends beyond simple file access bypasses to potentially enable more sophisticated attacks. Attackers can exploit this weakness to execute arbitrary PHP code by manipulating file paths in ways that circumvent access restrictions and validation checks. This could allow unauthorized users to gain access to sensitive files, execute malicious code on the server, or perform other unauthorized operations. The vulnerability is particularly dangerous because it can be exploited through common file operations like file_exists, which are frequently used in web applications for access control decisions. The attack vector is context-dependent, meaning that the effectiveness of exploitation depends on how the vulnerable PHP functions are used within the application. Security researchers have noted that this vulnerability aligns with ATT&CK technique T1059.007 for PHP, where adversaries use PHP-specific vulnerabilities to execute malicious code. The impact is amplified in environments where PHP applications perform file operations without proper input sanitization.
Mitigation strategies for this vulnerability require immediate patching of affected PHP installations to version 5.3.4 or later, where the null byte handling has been corrected. Organizations should implement comprehensive input validation and sanitization for all file path operations, ensuring that null characters are properly rejected or escaped. Additional defensive measures include configuring PHP with appropriate security settings such as disabling dangerous functions, implementing proper access controls, and using web application firewalls to detect and block suspicious file operations. Security teams should conduct thorough vulnerability assessments to identify all applications using affected PHP versions and ensure proper patch management procedures are in place. The vulnerability highlights the importance of proper string handling in security-sensitive applications and demonstrates why secure coding practices must address edge cases in input processing. Organizations should also consider implementing runtime monitoring and anomaly detection to identify potential exploitation attempts. Regular security audits and code reviews focusing on file path handling and string processing can help prevent similar vulnerabilities from being introduced in future development cycles.