CVE-2006-5307 in Guestbook
Summary
by MITRE
Multiple PHP remote file inclusion vulnerabilities in AFGB GUESTBOOK 2.2 allow remote attackers to execute arbitrary PHP code via a URL in the Htmls parameter in (1) add.php, (2) admin.php, (3) look.php, or (4) re.php.
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Analysis
by VulDB Data Team • 04/24/2026
The CVE-2006-5307 vulnerability represents a critical remote file inclusion flaw affecting AFGB GUESTBOOK version 2.2, which falls under the broader category of insecure direct object references and remote code execution vulnerabilities. This vulnerability stems from improper input validation and sanitization within the application's handling of user-supplied parameters, specifically the Htmls parameter that is processed across multiple script files including add.php, admin.php, look.php, and re.php. The flaw enables attackers to inject malicious URLs that are then included and executed as PHP code on the target server, creating a pathway for arbitrary code execution and complete system compromise.
The technical exploitation of this vulnerability occurs through the manipulation of the Htmls parameter, which is directly incorporated into the application's file inclusion mechanisms without proper validation or sanitization. When an attacker supplies a malicious URL as the Htmls parameter value, the vulnerable application processes this input and attempts to include the remote file, effectively executing any PHP code contained within the remote resource. This vulnerability is classified as a remote file inclusion (RFI) issue under CWE-88, which specifically addresses situations where user-controllable input is used to construct file paths or URLs that are then included in the application's execution flow. The vulnerability's impact is amplified by the fact that it affects multiple entry points within the application, providing attackers with several potential attack vectors to exploit.
From an operational perspective, this vulnerability presents a severe risk to systems running the affected AFGB GUESTBOOK version, as it allows remote attackers to execute arbitrary code with the privileges of the web server process. The implications extend beyond simple code execution to include potential data theft, system compromise, and the ability to establish persistent backdoors within the affected environment. The vulnerability's presence in multiple files increases the attack surface and reduces the effectiveness of simple input validation measures, as attackers can choose the most suitable entry point based on their target system's configuration and available resources. This type of vulnerability is particularly dangerous in the context of the MITRE ATT&CK framework, specifically relating to the T1059.007 technique for command and scripting interpreter, and the T1190 technique for exploit public-facing application, which both describe how attackers can leverage such vulnerabilities to gain unauthorized access and execute malicious code.
The mitigation strategies for CVE-2006-5307 require immediate implementation of several security controls to prevent exploitation. The most effective approach involves implementing strict input validation and sanitization measures that prevent user-controllable parameters from being used in file inclusion operations. Applications should avoid directly incorporating user input into file path constructions, instead implementing a whitelist-based approach that only allows pre-approved values. Additionally, the disable_functions directive in PHP configuration should be used to restrict potentially dangerous functions, and the allow_url_include directive should be set to off to prevent remote file inclusion altogether. Organizations should also implement network-based security controls such as web application firewalls that can detect and block malicious requests attempting to exploit this vulnerability, while regular security audits and vulnerability assessments should be conducted to identify similar issues in other applications within the organization's infrastructure. The vulnerability demonstrates the critical importance of proper input validation and the principle of least privilege in application security design, as it could have been prevented through basic security development practices that align with industry standards and best practices established in security frameworks like the OWASP Top Ten and NIST cybersecurity guidelines.