CVE-2007-4596 in PHP
Summary
by MITRE
The perl extension in PHP does not follow safe_mode restrictions, which allows context-dependent attackers to execute arbitrary code via the Perl eval function. NOTE: this might only be a vulnerability in limited environments.
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Analysis
by VulDB Data Team • 10/01/2024
The vulnerability identified as CVE-2007-4596 represents a critical security flaw in PHP's perl extension that directly undermines the intended security boundaries established by the safe_mode directive. This issue manifests when the perl extension fails to properly enforce the safe_mode restrictions that are designed to limit the execution environment and prevent unauthorized code execution. The vulnerability specifically affects the Perl eval function within PHP's perl extension, creating a potential attack vector that allows context-dependent malicious actors to bypass security controls and execute arbitrary code on the affected system. The nature of this vulnerability is particularly concerning because it operates at the intersection of two different programming environments, leveraging the integration between PHP and Perl to create an unexpected execution path.
The technical implementation of this flaw stems from the perl extension's inadequate handling of safe_mode restrictions when processing Perl code through the eval function. When PHP's safe_mode is enabled, it typically restricts file operations and function calls to prevent unauthorized access to system resources and execution of potentially harmful code. However, the perl extension in question does not properly validate or enforce these restrictions, allowing attackers to inject malicious Perl code that gets executed within the context of the web server process. This creates a situation where an attacker can leverage the perl extension's functionality to circumvent the intended security boundaries, effectively providing a backdoor mechanism for code execution. The vulnerability's context-dependent nature means that successful exploitation requires specific environmental conditions, including the presence of the perl extension and proper configuration of PHP's safe_mode settings.
The operational impact of CVE-2007-4596 extends beyond simple code execution, as it represents a fundamental breakdown in PHP's security model and can lead to complete system compromise. When exploited successfully, attackers can gain unauthorized access to server resources, potentially leading to data theft, system infiltration, or further exploitation of network services. The vulnerability's limited environment dependency suggests that it may only affect specific server configurations where the perl extension is installed and enabled, but this does not diminish its potential impact on affected systems. Organizations running PHP applications that utilize the perl extension in environments where safe_mode is expected to provide protection face significant risk of unauthorized code execution and potential complete system compromise. The vulnerability also highlights the importance of proper security boundary enforcement when integrating different programming environments and underscores the need for comprehensive security testing of extension modules.
Mitigation strategies for CVE-2007-4596 should focus on immediate remediation actions and long-term architectural considerations. The most effective immediate solution involves disabling the perl extension in PHP configurations where it is not absolutely required, as this eliminates the attack surface entirely. Organizations should also ensure that safe_mode is properly configured and that additional security measures such as open_basedir restrictions are implemented to provide layered protection. The vulnerability aligns with CWE-284, which addresses improper access control, and can be mapped to ATT&CK technique T1059.007 for execution through scripting languages, demonstrating how this flaw fits within broader cybersecurity frameworks. Regular security audits and vulnerability assessments should include checks for unnecessary PHP extensions, as the presence of the perl extension in production environments without proper security controls creates a significant risk. Additionally, organizations should consider upgrading to newer PHP versions where such integration issues have been addressed and security boundaries properly enforced.