CVE-2009-3559 in PHP
Summary
by MITRE
** DISPUTED ** main/streams/plain_wrapper.c in PHP 5.3.x before 5.3.1 does not recognize the safe_mode_include_dir directive, which allows context-dependent attackers to have an unknown impact by triggering the failure of PHP scripts that perform include or require operations, as demonstrated by a script that attempts to perform a require_once on a file in a standard library directory. NOTE: a reliable third party reports that this is not a vulnerability, because it results in a more restrictive security policy.
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Analysis
by VulDB Data Team • 02/02/2025
The vulnerability described in CVE-2009-3559 relates to a security flaw in PHP version 5.3.x before 5.3.1 where the main/streams/plain_wrapper.c component fails to properly recognize the safe_mode_include_dir directive. This issue exists within the PHP runtime environment's stream handling mechanisms and specifically affects how the system processes include and require operations. The vulnerability manifests when PHP scripts attempt to perform include or require operations on files located in standard library directories, creating a scenario where the security restrictions intended by the safe_mode_include_dir directive are bypassed or ignored.
From a technical perspective, this vulnerability represents a failure in the PHP security model's implementation of safe mode restrictions. The safe_mode_include_dir directive is designed to limit the directories from which files can be included or required when safe mode is enabled, thereby preventing unauthorized access to system resources. When this directive is not properly recognized by the plain_wrapper.c component, it allows attackers to bypass these intended restrictions. The flaw operates at the stream wrapper level where PHP handles file operations, making it particularly concerning as it affects fundamental file inclusion mechanisms that are used extensively throughout PHP applications.
The operational impact of this vulnerability, while disputed by some security researchers, remains significant in certain contexts. The vulnerability creates a situation where context-dependent attackers can potentially trigger failures in PHP scripts that would otherwise be protected by safe mode restrictions. This could lead to unintended behavior in applications that rely on the safe_mode_include_dir directive for security enforcement, potentially allowing unauthorized file access or execution of code in directories that should be restricted. The vulnerability specifically impacts require_once operations and other file inclusion mechanisms, making it particularly dangerous in applications that use these constructs extensively.
According to industry standards and security frameworks, this issue aligns with CWE-276, which deals with incorrect permissions for critical resources, and relates to the broader category of privilege escalation vulnerabilities. The ATT&CK framework would classify this under privilege escalation techniques where adversaries exploit misconfigurations to gain access to restricted resources. The disputed nature of this vulnerability stems from the fact that some security researchers argue that the behavior actually results in a more restrictive security policy rather than a weakening of security measures. This interpretation suggests that the vulnerability may not actually create new attack vectors but rather exposes existing security mechanisms in a way that some consider to be more restrictive than intended.
The recommended mitigation for this vulnerability involves upgrading to PHP version 5.3.1 or later, where the issue has been addressed through proper implementation of the safe_mode_include_dir directive recognition. Organizations should also review their PHP configurations to ensure that safe mode restrictions are properly enforced and that applications are not relying on potentially flawed security mechanisms. Additionally, security teams should monitor for any applications that might be affected by this behavior and verify that their security policies are functioning as intended. The vulnerability demonstrates the importance of proper stream wrapper implementation and the need for thorough testing of security features in web application frameworks.