CVE-2021-24191 in WP Maintenance Mode & Site Under Construction Plugin
Summary
by MITRE • 05/14/2021
Low privileged users can use the AJAX action 'cp_plugins_do_button_job_later_callback' in the WP Maintenance Mode & Site Under Construction WordPress plugin before 1.8.2, to install any plugin (including a specific version) from the WordPress repository, as well as activate arbitrary plugin from then blog, which helps attackers install vulnerable plugins and could lead to more critical vulnerabilities like RCE.
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Analysis
by VulDB Data Team • 05/16/2021
The vulnerability identified as CVE-2021-24191 affects the WP Maintenance Mode & Site Under Construction WordPress plugin, specifically targeting versions prior to 1.8.2. This security flaw represents a critical privilege escalation issue that allows low-privileged users to execute arbitrary plugin installation and activation operations through a specially crafted AJAX request. The vulnerability exists within the plugin's callback mechanism designated as 'cp_plugins_do_button_job_later_callback', which processes user inputs without adequate authorization checks or input sanitization. This oversight creates a significant attack surface where malicious actors with minimal privileges can leverage the plugin's functionality to compromise the entire WordPress installation.
The technical implementation of this vulnerability stems from insufficient access control mechanisms within the plugin's AJAX handling code. When a user submits a request to the 'cp_plugins_do_button_job_later_callback' endpoint, the system fails to verify whether the requesting user possesses the necessary administrative privileges to perform plugin installation or activation actions. This absence of proper authentication checks creates a direct pathway for privilege escalation, allowing users with capabilities such as contributor or author roles to execute operations typically restricted to administrators. The vulnerability is classified under CWE-284 Access Control Issues, specifically manifesting as improper access control in web applications. According to the ATT&CK framework, this represents a privilege escalation technique that can be categorized under T1068, which involves the exploitation of legitimate credentials to gain elevated access within a system.
The operational impact of this vulnerability extends beyond simple privilege escalation, creating potential pathways for more severe security compromises within WordPress environments. Attackers can leverage this vulnerability to install malicious plugins from the WordPress repository, potentially deploying plugins with known vulnerabilities or backdoors that could lead to remote code execution. The ability to activate arbitrary plugins provides attackers with persistent access mechanisms that can remain undetected for extended periods. Additionally, the vulnerability enables attackers to install specific plugin versions, allowing for targeted exploitation of known vulnerabilities in particular plugin releases. This capability significantly increases the attack surface and potential for cascading security breaches, as compromised WordPress installations can serve as entry points for broader network infiltration.
Organizations affected by CVE-2021-24191 should implement immediate remediation measures including updating the WP Maintenance Mode & Site Under Construction plugin to version 1.8.2 or later, which contains the necessary patches to address the access control flaw. Security administrators should also conduct thorough audits of their WordPress installations to identify any unauthorized plugin installations that may have occurred during the vulnerability window. Network monitoring solutions should be configured to detect anomalous AJAX requests targeting the affected plugin endpoints, as these activities could indicate exploitation attempts. The vulnerability demonstrates the critical importance of proper input validation and access control implementation in web applications, particularly in content management systems where plugins extend core functionality. Security teams should also consider implementing additional layers of protection such as web application firewalls and privileged access management controls to mitigate similar vulnerabilities across their WordPress environments. Regular security assessments and plugin vulnerability scanning should be conducted to identify and remediate similar access control issues before they can be exploited by malicious actors.