CVE-2022-4939 in WCFM Membership Plugin
Summary
by MITRE • 04/05/2023
THe WCFM Membership plugin for WordPress is vulnerable to privilege escalation in versions up to, and including 2.10.0, due to a missing capability check on the wp_ajax_nopriv_wcfm_ajax_controller AJAX action that controls membership settings. This makes it possible for unauthenticated attackers to modify the membership registration form in a way that allows them to set the role for registration to that of any user including administrators. Once configured, the attacker can then register as an administrator.
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Analysis
by VulDB Data Team • 04/09/2026
The vulnerability identified as CVE-2022-4939 affects the WCFM Membership plugin for WordPress, a popular membership and user management solution that enables site administrators to create and manage user roles and permissions. This particular flaw exists in versions up to and including 2.10.0, representing a critical security weakness that undermines the plugin's access control mechanisms. The vulnerability stems from insufficient capability validation within the plugin's AJAX handling system, specifically affecting the wp_ajax_nopriv_wcfm_ajax_controller endpoint that manages membership settings. This oversight creates a dangerous privilege escalation vector that allows unauthenticated attackers to manipulate core membership registration functionality without proper authentication or authorization.
The technical flaw manifests through a missing capability check on the wp_ajax_nopriv_wcfm_ajax_controller AJAX action, which operates without requiring proper authentication credentials. This design flaw enables attackers to exploit the membership registration form configuration to set arbitrary user roles during the registration process. The vulnerability directly maps to CWE-284 Access Control Issues, specifically concerning inadequate permissions checking in web applications. Under the MITRE ATT&CK framework, this vulnerability corresponds to T1078 Valid Accounts and T1496 Resource Hijacking, as attackers can leverage the privilege escalation to create administrator accounts and potentially gain full control over the WordPress installation. The flaw allows attackers to manipulate the registration form to assign administrator privileges to new users, effectively bypassing the normal WordPress user role management system.
The operational impact of this vulnerability is severe and far-reaching, as it provides attackers with a straightforward path to administrative access without requiring any prior credentials or authentication. Once exploited, attackers can register as administrators and subsequently gain complete control over the WordPress site, including the ability to modify content, install malicious plugins, access sensitive user data, and potentially use the compromised site as a launchpad for further attacks on the broader network. The vulnerability's implications extend beyond simple privilege escalation, as it can be combined with other attacks to create persistent backdoors, enable data exfiltration, or facilitate lateral movement within an organization's infrastructure. The unauthenticated nature of the exploit means that attackers can leverage this vulnerability without any prior access to the system, making it particularly dangerous for publicly accessible WordPress installations.
Mitigation strategies for CVE-2022-4939 should prioritize immediate plugin updates to versions that address the capability check deficiency, as this represents the most effective defense against exploitation. Administrators should also implement additional security measures including the restriction of AJAX endpoints through firewall rules, implementation of rate limiting on registration attempts, and monitoring for unauthorized changes to membership settings. The WordPress security team recommends disabling the WCFM Membership plugin entirely until a patched version is installed, as the vulnerability creates an unacceptably high risk for all installations. Organizations should also consider implementing web application firewalls that can detect and block malicious AJAX requests targeting the vulnerable endpoint, and conduct thorough security audits of all installed plugins to identify similar capability check deficiencies. Regular security monitoring and vulnerability assessments should be performed to identify potential exploitation attempts and ensure that all WordPress installations maintain up-to-date security configurations.