CVE-2006-6764 in Keep It Simple Guest Book
Summary
by MITRE
PHP remote file inclusion vulnerability in authenticate.php in Keep It Simple Guest Book (KISGB), when executing PHP through CGI, allows remote attackers to execute arbitrary PHP code via a URL in the default_path_to_themes parameter.
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Analysis
by VulDB Data Team • 12/21/2024
The vulnerability identified as CVE-2006-6764 represents a critical remote file inclusion flaw in the Keep It Simple Guest Book (KISGB) web application, specifically within the authenticate.php script. This vulnerability arises from improper input validation and sanitization mechanisms that fail to properly restrict user-supplied data before incorporating it into the application's execution flow. The flaw manifests when the application processes the default_path_to_themes parameter through a CGI interface, creating an attack vector that enables remote adversaries to inject malicious file paths.
The technical implementation of this vulnerability stems from the application's failure to validate or sanitize the default_path_to_themes parameter, which is directly incorporated into file inclusion operations without adequate security controls. When PHP executes through CGI mode, the vulnerability becomes exploitable because the CGI interface does not provide the same security context as native PHP execution. Attackers can craft malicious URLs containing arbitrary PHP code within the default_path_to_themes parameter, which gets executed by the web server when the vulnerable script processes the request. This type of vulnerability falls under the CWE-98 category of Improper Input Validation and maps to ATT&CK technique T1190 for exploiting weaknesses in web applications.
The operational impact of this vulnerability is severe as it allows remote attackers to execute arbitrary PHP code on the target system with the privileges of the web server process. Successful exploitation can lead to complete system compromise, data exfiltration, lateral movement within the network, and establishment of persistent backdoors. The vulnerability affects installations where KISGB is deployed with PHP CGI execution mode, which was common in shared hosting environments during the time of the vulnerability's discovery. The attack requires minimal privileges and can be executed through standard web browser interactions, making it particularly dangerous for public-facing web applications.
Mitigation strategies for CVE-2006-6764 should focus on immediate patching of the affected KISGB version, implementation of input validation controls, and configuration changes to prevent remote file inclusion attacks. Organizations should disable remote file inclusion capabilities in PHP configurations using directives such as allow_url_fopen and allow_url_include set to off. Additionally, parameter validation should be implemented to ensure that the default_path_to_themes parameter only accepts expected local file paths without URL schemes or remote references. Network-level protections such as web application firewalls and intrusion prevention systems should be configured to monitor and block suspicious URL patterns. The vulnerability demonstrates the importance of proper input sanitization and the principle of least privilege in web application security, aligning with security frameworks that emphasize defense in depth and secure coding practices.