CVE-2023-0816 in Formidable Forms Plugin
Summary
by MITRE • 03/27/2023
The Formidable Forms WordPress plugin before 6.1 uses several potentially untrusted headers to determine the IP address of the client, leading to IP Address spoofing and bypass of anti-spam protections.
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Analysis
by VulDB Data Team • 04/04/2023
The Formidable Forms WordPress plugin vulnerability CVE-2023-0816 represents a critical security flaw in version 6.1 and earlier that undermines the integrity of client IP address identification mechanisms. This vulnerability stems from the plugin's reliance on potentially untrusted HTTP headers to determine user IP addresses, creating a pathway for malicious actors to manipulate or forge client identification information. The issue directly impacts the plugin's ability to maintain accurate session tracking and anti-spam protection measures that depend on legitimate IP address validation.
The technical implementation of this vulnerability occurs through the plugin's improper handling of HTTP headers such as X-Forwarded-For, X-Real-IP, and other similar fields that are commonly used to determine client IP addresses in web applications. These headers can be easily manipulated by attackers who control the network path or have access to the client-side request processing. When the plugin accepts these headers without proper validation or sanitization, it creates an environment where spoofed IP addresses can be accepted as legitimate, effectively bypassing any IP-based security controls that the plugin or WordPress itself might implement.
From an operational impact perspective, this vulnerability enables several serious attack vectors including spam form submissions, brute force attack bypass, and unauthorized access attempts that would otherwise be blocked by IP-based restrictions. The vulnerability specifically undermines the anti-spam protections that form the foundation of many WordPress security implementations, allowing malicious actors to flood forms with spam submissions or conduct targeted attacks without facing the IP-based rate limiting or blocking mechanisms that should otherwise protect the system. This creates a significant risk for websites relying on Formidable Forms for contact forms, registration systems, or any other form-based functionality that depends on IP address validation for security purposes.
The vulnerability aligns with CWE-284 Access Control Issues and specifically relates to improper input validation in header processing. From an attack framework perspective, this flaw maps to multiple ATT&CK techniques including T1566 Credential Access and T1071.1001 Application Layer Protocol. The attack surface is particularly concerning because it affects a widely used WordPress plugin that many websites depend upon for form handling, making the potential impact widespread across various web applications. Organizations using this plugin face a heightened risk of automated abuse, including form spamming, data harvesting, and potential exploitation of other security controls that depend on accurate IP address information. The vulnerability demonstrates a fundamental flaw in the plugin's security architecture where trust is placed in potentially manipulable HTTP headers without proper verification mechanisms.
The recommended mitigation strategy involves upgrading to Formidable Forms version 6.1 or later, which includes proper IP address validation and sanitization mechanisms. Organizations should also implement additional security layers including rate limiting, CAPTCHA integration, and proper input validation at the web server level. Network administrators should consider implementing additional monitoring for suspicious form submission patterns and ensure that IP-based security controls are properly configured at multiple levels of the application stack. The vulnerability highlights the importance of implementing defense-in-depth strategies where no single method of IP address determination is relied upon exclusively, and where multiple validation checks are performed to ensure the authenticity of client identification information.