CVE-2021-24790 in Contact Form Advanced Database Plugin
Summary
by MITRE • 12/13/2021
The Contact Form Advanced Database WordPress plugin through 1.0.8 does not have any authorisation as well as CSRF checks in its delete_cf7_data and export_cf7_data AJAX actions, available to any authenticated users, which could allow users with a role as low as subscriber to call them. The delete_cf7_data would lead to arbitrary metadata deletion, as well as PHP Object Injection if a suitable gadget chain is present in another plugin, as user data is passed to the maybe_unserialize() function without being first validated.
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Analysis
by VulDB Data Team • 12/15/2021
The vulnerability identified as CVE-2021-24790 affects the Contact Form Advanced Database WordPress plugin version 1.0.8 and earlier, presenting a critical security flaw that undermines the plugin's access control mechanisms. This issue stems from the absence of proper authorization and cross-site request forgery protection within two specific AJAX actions: delete_cf7_data and export_cf7_data. The flaw allows any authenticated user, regardless of their role within the WordPress system, to exploit these functions, creating a significant privilege escalation vector that can be leveraged by low-privilege users such as subscribers.
The technical implementation of this vulnerability resides in the plugin's failure to validate user permissions before executing sensitive operations. When an authenticated user accesses these AJAX endpoints, the plugin processes the requests without verifying whether the user possesses the necessary administrative privileges or if the request originates from a legitimate source. This lack of validation creates a pathway for unauthorized manipulation of contact form data, with the delete_cf7_data function specifically enabling arbitrary metadata deletion that can compromise the integrity of stored user information.
The operational impact of this vulnerability extends beyond simple data manipulation, as it introduces potential for more severe consequences through PHP Object Injection vulnerabilities. When user data is passed to the maybe_unserialize() function without proper validation, the system becomes susceptible to deserialization attacks if other plugins contain suitable gadget chains. This creates an attack surface that can be exploited to execute arbitrary code on the target system, potentially leading to complete compromise of the WordPress installation. The vulnerability aligns with CWE-863, which addresses "Incorrect Authorization," and represents a classic example of insufficient access control in web applications.
The security implications of this vulnerability are particularly concerning given that it affects a widely used WordPress plugin and requires minimal privileges to exploit. Attackers with subscriber-level access can leverage these functions to delete critical contact form data, potentially disrupting business operations and compromising sensitive information. The PHP Object Injection aspect of the vulnerability, while requiring additional conditions to be exploitable, significantly increases the potential impact by providing a means to execute arbitrary code within the WordPress environment. Organizations should consider this vulnerability in the context of ATT&CK technique T1078 which covers valid accounts and T1566 which covers credential harvesting, as the low privilege requirement makes it particularly attractive for attackers seeking persistent access.
Mitigation strategies for this vulnerability should include immediate patching of the affected plugin to version 1.0.9 or later, which addresses the authorization and CSRF protection gaps. Administrators should also implement additional security measures such as monitoring for unauthorized access attempts to AJAX endpoints and reviewing user roles to ensure that only trusted users have access to sensitive functions. Network-level protections including web application firewalls and request rate limiting can provide additional defense in depth. Organizations should conduct comprehensive security audits of their WordPress installations to identify similar vulnerabilities in other plugins and themes, as this type of authorization flaw is commonly found in poorly secured WordPress components. The vulnerability demonstrates the critical importance of implementing proper access controls and CSRF protection mechanisms in web applications, particularly those handling user data and providing administrative functions through AJAX interfaces.