CVE-2016-6897 in WordPress
Summary
by MITRE
Cross-site request forgery (CSRF) vulnerability in the wp_ajax_update_plugin function in wp-admin/includes/ajax-actions.php in WordPress before 4.6 allows remote attackers to hijack the authentication of subscribers for /dev/random read operations by leveraging a late call to the check_ajax_referer function, a related issue to CVE-2016-6896.
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Analysis
by VulDB Data Team • 05/13/2026
The CVE-2016-6897 vulnerability represents a critical cross-site request forgery flaw within the WordPress content management system that specifically targets the wp_ajax_update_plugin function in the wp-admin/includes/ajax-actions.php file. This vulnerability affects WordPress versions prior to 4.6 and exploits a timing issue in the authentication verification process that allows attackers to manipulate authenticated sessions. The flaw occurs due to a late invocation of the check_ajax_referer function, which creates a window of opportunity for malicious actors to exploit the system's security mechanisms. This vulnerability is particularly concerning because it specifically targets subscriber-level users, who typically have limited privileges but can still be exploited to perform unauthorized operations within the WordPress administrative interface.
The technical implementation of this CSRF vulnerability stems from the improper sequence of security checks within the WordPress AJAX handling mechanism. When a user with subscriber privileges makes an AJAX request to update a plugin, the system should validate the request's authenticity before processing any operations. However, the check_ajax_referer function is called too late in the execution flow, allowing an attacker to craft a malicious request that appears legitimate to the system. This flaw operates under the principle that the system should validate all incoming requests before executing any potentially dangerous operations, a fundamental security principle that WordPress failed to implement properly in this specific function. The vulnerability enables attackers to perform operations that would normally require valid authentication tokens, effectively allowing them to hijack the authenticated sessions of subscribers.
The operational impact of CVE-2016-6897 extends beyond simple unauthorized access, as it allows attackers to leverage the compromised subscriber accounts to perform various malicious activities within the WordPress environment. Since subscribers can execute plugin update operations, an attacker who successfully hijacks such a session could potentially install malicious plugins, modify existing plugins, or perform other operations that could compromise the entire website. This vulnerability is particularly dangerous because it operates at the administrative level where legitimate users expect to be protected from unauthorized modifications. The fact that this issue is related to CVE-2016-6896 demonstrates a pattern of similar timing-based authentication flaws that affect WordPress's AJAX security mechanisms, suggesting a broader systemic issue in how the platform handles cross-site request verification.
Organizations and WordPress administrators should prioritize immediate remediation by upgrading to WordPress version 4.6 or later, which contains the necessary patches to address this CSRF vulnerability. The fix implemented in version 4.6 properly repositions the check_ajax_referer function call to occur earlier in the execution flow, ensuring that all AJAX requests are validated before any processing begins. Additionally, administrators should implement additional security measures such as monitoring for unusual plugin update activities, implementing rate limiting on AJAX requests, and ensuring that all users have appropriate privilege levels. This vulnerability aligns with CWE-352, which specifically addresses Cross-Site Request Forgery weaknesses, and demonstrates how improper sequence of security checks can create exploitable conditions. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, as attackers can leverage lower-privilege accounts to perform unauthorized administrative actions, making it a significant concern for WordPress security posture management.