CVE-2002-0253 in PHP
Summary
by MITRE
PHP, when not configured with the "display_errors = Off" setting in php.ini, allows remote attackers to obtain the physical path for an include file via a trailing slash in a request to a directly accessible PHP program, which modifies the base path, causes the include directive to fail, and produces an error message that contains the path.
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Analysis
by VulDB Data Team • 04/26/2017
This vulnerability exists in php versions prior to 4.1.2 and 4.2.3 where the display_errors directive is enabled in php.ini configuration. The flaw occurs when php applications are configured to display error messages to remote users, creating a path disclosure scenario that can reveal sensitive system information. When an attacker crafts a request with a trailing slash to a PHP script that includes files, the base path calculation becomes modified, causing include directives to fail and generate error messages containing the physical file paths on the server. This vulnerability is classified under CWE-209, which deals with information exposure through error message, and represents a classic path disclosure attack vector. The vulnerability allows attackers to gain knowledge about the server filesystem structure which can be leveraged for further exploitation.
The technical mechanism behind this vulnerability involves the interaction between PHP's include functionality and error reporting settings. When display_errors is set to On, PHP will output error messages to the client when include operations fail. The specific condition occurs when a trailing slash is appended to a request URI that points to a PHP file, which causes PHP to modify the base path used for include operations. This modification results in include directives failing and generating error messages that contain the full physical path to the include file, effectively leaking system information to unauthorized users. The vulnerability demonstrates the dangerous practice of exposing internal server paths through error messages, which violates security best practices for information hiding.
The operational impact of this vulnerability is significant as it provides attackers with valuable reconnaissance information about the target system. The leaked physical paths can reveal directory structures, file locations, and potentially sensitive information about the server environment that could be used in subsequent attacks. Attackers can use this information to craft more targeted attacks, identify potential file inclusion vulnerabilities, or map the server filesystem for further exploitation. This vulnerability directly impacts the principle of least privilege and information hiding, as it exposes internal system details that should remain confidential. The vulnerability can be exploited as part of a broader attack chain, potentially leading to more severe consequences such as remote code execution or privilege escalation.
The recommended mitigations for this vulnerability include configuring PHP with display_errors = Off in the php.ini file to prevent error messages from being displayed to remote users. Additionally, implementing proper input validation and sanitization for file inclusion parameters can help prevent exploitation. Organizations should also consider implementing proper error handling mechanisms that do not expose sensitive information in error messages. This vulnerability aligns with ATT&CK technique T1082, which covers system information discovery, and T1190, which involves exploitation of remote services. Regular security audits and proper configuration management are essential to prevent such vulnerabilities from being exploited in production environments. The vulnerability highlights the importance of secure coding practices and proper security configuration management in preventing information disclosure attacks.