CVE-2015-8351 in Gwolle Guestbook Plugin
Summary
by MITRE
PHP remote file inclusion vulnerability in the Gwolle Guestbook plugin before 1.5.4 for WordPress, when allow_url_include is enabled, allows remote authenticated users to execute arbitrary PHP code via a URL in the abspath parameter to frontend/captcha/ajaxresponse.php. NOTE: this can also be leveraged to include and execute arbitrary local files via directory traversal sequences regardless of whether allow_url_include is enabled.
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Analysis
by VulDB Data Team • 02/16/2025
The vulnerability CVE-2015-8351 represents a critical remote file inclusion flaw in the Gwolle Guestbook WordPress plugin affecting versions prior to 1.5.4. This vulnerability exists within the frontend/captcha/ajaxresponse.php file and specifically targets the abspath parameter handling. The issue manifests when the PHP configuration allows remote file inclusion through the allow_url_include directive, creating a pathway for malicious actors to execute arbitrary code on affected systems. The vulnerability operates at the intersection of improper input validation and insecure file handling practices, making it particularly dangerous in web application environments.
The technical exploitation of this vulnerability occurs through a combination of parameter manipulation and directory traversal techniques. When an authenticated user accesses the vulnerable endpoint with a malicious abspath parameter containing a URL, the plugin fails to properly validate or sanitize the input before using it in file inclusion operations. This allows attackers to specify remote URLs that contain malicious PHP code, which gets executed on the target server. The vulnerability's design flaw stems from CWE-22, which addresses improper limitation of a pathname to a restricted directory, and CWE-434, which covers unsanitized upload of file with dangerous type. The attack vector is particularly insidious because it leverages legitimate WordPress plugin functionality while bypassing normal security controls through crafted input parameters.
The operational impact of this vulnerability extends beyond simple code execution to encompass full system compromise capabilities. Attackers can leverage the vulnerability to execute arbitrary commands on the affected server, potentially leading to complete system takeover, data exfiltration, or deployment of additional malware. The vulnerability's ability to work both with and without allow_url_include enabled makes it particularly dangerous as it removes the need for specific PHP configuration changes to exploit the flaw. This characteristic places the vulnerability in the ATT&CK framework under T1059 for command and scripting interpreter and T1105 for remote file inclusion techniques. The authenticated nature of the attack means that even a low-privilege user account can potentially exploit this vulnerability, making it a significant concern for WordPress administrators who may not properly monitor user activities.
Mitigation strategies for CVE-2015-8351 require immediate plugin updates to version 1.5.4 or later, which addresses the input validation flaws in the affected file. System administrators should also implement proper input sanitization measures and disable allow_url_include in PHP configurations when possible. Additional defensive measures include implementing web application firewalls to detect and block malicious parameter patterns, monitoring for unusual file inclusion activities, and conducting regular security audits of installed WordPress plugins. The vulnerability highlights the importance of proper parameter validation and secure coding practices in WordPress plugin development, particularly regarding file handling operations. Organizations should also consider implementing principle of least privilege access controls and regular security assessments to identify similar vulnerabilities in their WordPress installations. The remediation process must include thorough testing of the updated plugin to ensure that the vulnerability has been properly addressed without introducing new issues.