CVE-2019-11557 in Contact Form Builder Plugin
Summary
by MITRE
The WebDorado Contact Form Builder plugin before 1.0.69 for WordPress allows CSRF via the wp-admin/admin-ajax.php action parameter, with resultant local file inclusion via directory traversal, because there can be a discrepancy between the $_POST['action'] value and the $_GET['action'] value, and the latter is unsanitized.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/07/2023
The CVE-2019-11557 vulnerability represents a critical security flaw in the WebDorado Contact Form Builder plugin for WordPress affecting versions prior to 1.0.69. This vulnerability combines cross-site request forgery (CSRF) and local file inclusion (LFI) capabilities through a sophisticated manipulation of HTTP request parameters. The flaw exists within the wp-admin/admin-ajax.php endpoint which serves as a central processing point for WordPress AJAX requests, making it a prime target for attackers seeking to exploit plugin vulnerabilities. The vulnerability stems from an inconsistent handling of action parameters between POST and GET requests, creating a pathway for malicious actors to manipulate the application's behavior through crafted requests.
The technical implementation of this vulnerability exploits a fundamental flaw in parameter validation where the plugin processes $_POST['action'] and $_GET['action'] values independently without proper sanitization of the GET parameter. When an attacker crafts a malicious request that includes a directory traversal payload within the GET action parameter, the unsanitized value can be processed by the plugin's logic, leading to unauthorized file access. This discrepancy between POST and GET parameter handling creates a dangerous condition where an attacker can bypass normal validation mechanisms by leveraging the GET parameter's unsanitized nature. The vulnerability specifically targets the plugin's handling of AJAX requests and demonstrates poor input validation practices that violate secure coding principles.
The operational impact of CVE-2019-11557 is severe and multifaceted, as it allows attackers to perform local file inclusion attacks that can lead to arbitrary code execution, data theft, or complete system compromise. An attacker can leverage this vulnerability to read sensitive files from the server filesystem, potentially accessing configuration files, database credentials, or other critical system information. The combination of CSRF and LFI capabilities means that an attacker could not only manipulate the plugin's functionality but also gain access to the underlying server infrastructure. This vulnerability directly relates to CWE-79 and CWE-22, which address cross-site scripting and path traversal issues respectively, and aligns with ATT&CK technique T1213.002 for data from information repositories and T1059.001 for command and script injection.
Mitigation strategies for CVE-2019-11557 should prioritize immediate plugin updates to version 1.0.69 or later, which addresses the core parameter validation issue. Administrators should implement proper input sanitization for all AJAX endpoints and ensure that GET parameters are consistently validated against POST parameters when both are present. Network-level protections such as web application firewalls can help detect and block suspicious directory traversal patterns in URL parameters. Regular security auditing of WordPress plugins and themes should include verification of parameter handling practices, particularly around AJAX endpoints. The vulnerability highlights the importance of maintaining current security patches and implementing defense-in-depth strategies that include both application-level and network-level protections. Organizations should also consider implementing automated vulnerability scanning tools that can detect similar parameter handling issues across their WordPress installations.