CVE-2021-24278 in Redirection for Contact Form 7 Plugin
Summary
by MITRE • 05/14/2021
In the Redirection for Contact Form 7 WordPress plugin before 2.3.4, unauthenticated users can use the wpcf7r_get_nonce AJAX action to retrieve a valid nonce for any WordPress action/function.
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Analysis
by VulDB Data Team • 05/16/2021
The vulnerability identified as CVE-2021-24278 affects the Redirection for Contact Form 7 WordPress plugin, specifically versions prior to 2.3.4, presenting a significant security weakness that allows unauthenticated attackers to exploit a flaw in the plugin's nonce generation mechanism. This issue resides within the wpcf7r_get_nonce AJAX action which is designed to provide nonces for WordPress actions but fails to properly validate user authentication status. The flaw enables attackers to obtain valid nonces for arbitrary WordPress functions without requiring any authentication credentials, effectively bypassing WordPress's built-in security protections that rely on nonce validation.
The technical implementation of this vulnerability stems from inadequate access control within the plugin's AJAX handler. When an unauthenticated user accesses the wpcf7r_get_nonce endpoint, the plugin generates and returns a valid nonce without verifying whether the requester possesses legitimate authorization to perform the requested action. This design flaw allows malicious actors to harvest nonces that can subsequently be used to execute privileged operations within the WordPress environment. The vulnerability directly maps to CWE-284 Access Control Bypass, as it permits unauthorized users to gain access to resources that should require authentication. The flaw is particularly concerning because it operates at the core of WordPress's security architecture, where nonces serve as critical protection mechanisms against cross-site request forgery attacks.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to perform authenticated operations within the WordPress admin interface without proper credentials. An attacker could potentially use the harvested nonces to manipulate contact form configurations, modify plugin settings, or even execute administrative actions that could lead to complete compromise of the WordPress installation. The vulnerability enables a range of malicious activities including but not limited to unauthorized data modification, potential privilege escalation, and the ability to perform actions that would normally require administrator-level access. This represents a critical weakness in the plugin's security model and exposes WordPress sites to significant risk from unauthenticated attackers.
Security mitigations for this vulnerability involve immediate patching of the Redirection for Contact Form 7 plugin to version 2.3.4 or later, which addresses the improper access control by implementing proper authentication checks within the wpcf7r_get_nonce AJAX handler. Organizations should also implement additional defensive measures including monitoring for unauthorized access attempts to AJAX endpoints, implementing rate limiting on API calls, and conducting regular security audits of WordPress plugins to identify similar access control issues. The remediation aligns with ATT&CK technique T1213.002 Credential Access: Credentials in Files, as it addresses the exposure of valid authentication tokens through improper access controls. Additionally, administrators should consider implementing web application firewalls to monitor and block suspicious AJAX requests, and maintain updated security baselines that enforce proper authentication requirements for all plugin functionality. The vulnerability demonstrates the importance of proper input validation and access control implementation in WordPress plugin development, particularly when dealing with AJAX endpoints that may be exposed to unauthenticated users.