CVE-2008-6934 in Free simple guestbook PHP script
Summary
by MITRE
Static code injection vulnerability in Sanus|artificium (aka Sanusart) Free simple guestbook PHP script, when downloaded before 20081111, allows remote attackers to inject arbitrary PHP code into messages.txt via the message parameter to act.php, which is executed when guestbook/guestbook.php is accessed. NOTE: some of these details are obtained from third party information.
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Analysis
by VulDB Data Team • 11/10/2024
The vulnerability identified as CVE-2008-6934 represents a critical static code injection flaw within the Sanus|artificium free guestbook PHP script, specifically affecting versions downloaded prior to November 11, 2008. This vulnerability resides in the script's handling of user input through the message parameter in the act.php file, creating a persistent security risk that enables remote attackers to execute arbitrary PHP code within the target system's context. The flaw demonstrates a classic example of insufficient input validation and sanitization, where user-supplied data flows directly into the application's execution path without proper security measures.
The technical implementation of this vulnerability occurs through the improper handling of the message parameter in the act.php script, which accepts user input and writes it directly to the messages.txt file without any sanitization or encoding mechanisms. When subsequent visitors access the guestbook.php page, the malicious code contained within the messages.txt file gets executed as PHP code, effectively transforming the guestbook into a persistent backdoor for remote code execution. This represents a form of code injection vulnerability that aligns with CWE-94, which describes the execution of unrestricted code or commands, and specifically falls under the category of PHP code injection attacks that leverage stored input data.
The operational impact of this vulnerability extends far beyond simple data manipulation, as it provides attackers with complete control over the affected web server's execution environment. Remote attackers can leverage this vulnerability to execute arbitrary commands, potentially escalating privileges, accessing sensitive data, or using the compromised system as a launch point for further attacks within the network. The persistence of this vulnerability means that once exploited, the malicious code remains active until manually removed from the messages.txt file, creating a long-term security risk that can be exploited repeatedly by multiple attackers. This vulnerability directly maps to techniques described in the ATT&CK framework under the T1059.007 sub-technique for PHP, where adversaries leverage web applications to execute malicious code through injection attacks.
Mitigation strategies for this vulnerability require immediate action to address the root cause through proper input sanitization and output encoding mechanisms. System administrators should implement proper parameter validation that filters or escapes special characters in user input before storing it in persistent storage, particularly within the message parameter handling code. The recommended approach involves implementing a comprehensive input validation scheme that prevents PHP code execution by filtering out dangerous characters and sequences that could enable code injection. Additionally, the application should be updated to use secure coding practices that separate data storage from code execution, ensuring that user input stored in files like messages.txt cannot be executed as PHP code. Organizations should also consider implementing web application firewalls and regular security audits to detect and prevent similar vulnerabilities in other applications, while the specific remediation for this vulnerability would require replacing the vulnerable script with a secure version that properly validates and sanitizes all user input before processing or storing it within the application's data files.