CVE-2007-4528 in PHP
Summary
by MITRE
The Foreign Function Interface (ffi) extension in PHP 5.0.5 does not follow safe_mode restrictions, which allows context-dependent attackers to execute arbitrary code by loading an arbitrary DLL and calling a function, as demonstrated by kernel32.dll and the WinExec function. NOTE: this issue does not cross privilege boundaries in most contexts, so perhaps it should not be included in CVE.
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Analysis
by VulDB Data Team • 09/30/2024
The vulnerability identified as CVE-2007-4528 resides within the Foreign Function Interface extension of PHP version 5.0.5, representing a critical security flaw that undermines the intended privilege controls of the PHP runtime environment. This issue specifically targets the safe_mode restrictions that are fundamental to PHP's security architecture, creating a dangerous pathway for malicious actors to bypass these protective measures and execute unauthorized operations on vulnerable systems. The flaw manifests when the ffi extension fails to properly enforce the safe_mode limitations that should restrict file access and execution permissions, allowing attackers to circumvent these security controls through legitimate extension functionality.
The technical exploitation of this vulnerability involves leveraging the ffi extension's capability to dynamically load and execute external dynamic link libraries on Windows systems. Attackers can specifically target the loading of kernel32.dll and subsequently invoke the WinExec function, which provides the ability to execute arbitrary commands on the underlying operating system. This represents a direct violation of the principle of least privilege, as the extension operates outside the normal security boundaries that should prevent such unauthorized system interactions. The vulnerability essentially provides a backdoor mechanism through which attackers can execute arbitrary code with the privileges of the web server process, potentially leading to complete system compromise.
The operational impact of CVE-2007-4528 extends beyond simple code execution, as it represents a significant escalation of privileges within web application environments where PHP is deployed. The vulnerability allows attackers to bypass the intended security boundaries that separate different user contexts and system resources, potentially enabling them to access sensitive data, modify system configurations, or establish persistent access to compromised systems. The context-dependent nature of this vulnerability means that exploitation requires specific conditions to be met, including the presence of the vulnerable ffi extension and appropriate system configurations that allow DLL loading operations. However, the potential for privilege escalation makes this vulnerability particularly dangerous in production environments where PHP applications handle sensitive information and operate with elevated system privileges.
Security researchers categorize this vulnerability under CWE-250, which addresses the execution of code with improper privileges, and it aligns with ATT&CK technique T1059.007 for execution through dynamic-link libraries. The weakness demonstrates a failure in proper access control enforcement within the PHP runtime environment, where extension functionality should be subject to the same security restrictions as core PHP operations. Organizations affected by this vulnerability should immediately implement mitigations including disabling the ffi extension when not required, applying the appropriate PHP security patches, and implementing network segmentation to limit potential attack vectors. The vulnerability also underscores the importance of comprehensive security testing for extension modules and proper privilege management in web application environments, as it represents a failure in the security model that should prevent such cross-boundary execution scenarios.