CVE-2001-1247 in PHP
Summary
by MITRE
PHP 4.0.4pl1 and 4.0.5 in safe mode allows remote attackers to read and write files owned by the web server UID by uploading a PHP script that uses the error_log function to access the files.
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Analysis
by VulDB Data Team • 04/21/2017
The vulnerability identified as CVE-2001-1247 represents a critical security flaw in PHP versions 4.0.4pl1 and 4.0.5 that directly undermines the intended security boundaries of safe mode execution. This vulnerability specifically targets the error_log function's behavior within PHP's safe mode implementation, creating a path for remote attackers to bypass file access restrictions that should normally protect web server processes and their associated files. The flaw demonstrates a fundamental weakness in how PHP handled file operations when the error_log function was utilized in conjunction with the safe mode security context, effectively allowing unauthorized access to files that should only be accessible to the web server process itself.
The technical exploitation of this vulnerability occurs through a carefully crafted PHP script that leverages the error_log function to manipulate file access patterns. When PHP operates in safe mode, it typically restricts file operations to prevent unauthorized access to system resources, but the error_log function in these specific versions contained a flaw that allowed attackers to circumvent these restrictions. The vulnerability operates by having the attacker upload a malicious PHP script that utilizes error_log to create or modify files that are owned by the web server UID, effectively enabling the attacker to read and write to files that should normally be protected from such access. This mechanism violates the core principle of safe mode which is designed to prevent remote code execution and unauthorized file access by restricting file operations to the web server's user context.
The operational impact of CVE-2001-1247 extends beyond simple file access violations and represents a significant compromise of web server security that can lead to complete system compromise. Attackers can leverage this vulnerability to execute arbitrary code on the web server, potentially gaining access to sensitive data, modifying web content, or establishing persistent access points. The vulnerability particularly affects systems where PHP is used for web applications and where safe mode is enabled as a security measure, making it a critical concern for web administrators who rely on PHP's built-in security mechanisms. This flaw essentially renders the safe mode protection ineffective, undermining the security posture of affected systems and potentially enabling more sophisticated attacks that could escalate to full system compromise. The vulnerability's exploitation is relatively straightforward, requiring only the ability to upload a PHP script to the web server, making it particularly dangerous in environments where user upload capabilities exist.
The technical nature of this vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, and reflects the broader category of privilege escalation issues that have plagued web application security for decades. From an attack perspective, this vulnerability fits within the ATT&CK framework's privilege escalation and defense evasion tactics, as it allows attackers to bypass security controls that should restrict file access to web server processes. The vulnerability also demonstrates the importance of proper input validation and the dangers of relying on single-layer security mechanisms, as safe mode alone proved insufficient against this particular exploitation vector. Organizations affected by this vulnerability should immediately implement patches, disable vulnerable PHP installations, and review their file upload mechanisms to prevent exploitation. The remediation process should include comprehensive security audits of PHP applications, implementation of proper file access controls, and deployment of additional security measures such as web application firewalls to protect against similar vulnerabilities that may exist in other components of the web infrastructure.