CVE-2016-6896 in WordPress
Summary
by MITRE
Directory traversal vulnerability in the wp_ajax_update_plugin function in wp-admin/includes/ajax-actions.php in WordPress 4.5.3 allows remote authenticated users to cause a denial of service or read certain text files via a .. (dot dot) in the plugin parameter to wp-admin/admin-ajax.php, as demonstrated by /dev/random read operations that deplete the entropy pool.
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Analysis
by VulDB Data Team • 05/13/2026
The vulnerability identified as CVE-2016-6896 represents a directory traversal flaw within WordPress's administrative ajax handling mechanism. This issue exists in the wp_ajax_update_plugin function located in wp-admin/includes/ajax-actions.php within WordPress version 4.5.3, creating a significant security weakness that affects authenticated users with administrative privileges. The flaw stems from insufficient input validation when processing plugin parameters through the admin-ajax.php endpoint, which serves as the central hub for handling asynchronous requests in WordPress administration.
The technical implementation of this vulnerability allows attackers to exploit the lack of proper sanitization in the plugin parameter, enabling them to manipulate file paths through directory traversal sequences using the .. (dot dot) notation. When authenticated users with administrative access make requests to wp-admin/admin-ajax.php, the system fails to properly validate or sanitize the plugin parameter, creating an opportunity for malicious input to traverse the file system. This vulnerability specifically affects the wp_ajax_update_plugin function which handles plugin update operations, but the flaw extends beyond its intended scope due to improper path validation.
The operational impact of this vulnerability manifests in two primary ways: denial of service and unauthorized file reading capabilities. The most concerning aspect involves the ability to perform read operations on sensitive system files such as /dev/random, which serves as a critical entropy source for cryptographic operations. When attackers exploit this vulnerability to read from /dev/random, they can drain the system's entropy pool, leading to predictable cryptographic outputs and potentially compromising the security of encryption algorithms. This type of resource exhaustion attack can render the system vulnerable to various cryptographic attacks and may cause system instability or denial of service conditions.
The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal. This weakness allows attackers to access files and directories outside the intended scope, potentially leading to information disclosure, system compromise, or service disruption. From an attack framework perspective, this vulnerability maps to ATT&CK technique T1059, which involves executing commands through the command and scripting interpreter, as the directory traversal can be leveraged to execute arbitrary code or access sensitive system resources. The authenticated nature of this vulnerability means that attackers must first gain administrative credentials, but once achieved, they can leverage this flaw to cause significant damage to the system's integrity and availability.
Mitigation strategies for CVE-2016-6896 involve immediate patching of WordPress installations to versions that address this directory traversal vulnerability. System administrators should also implement additional security controls such as restricting access to wp-admin/admin-ajax.php through firewall rules or web application firewalls, implementing input validation at multiple layers, and monitoring for suspicious file access patterns. The WordPress core team addressed this issue in subsequent releases by adding proper input sanitization and validation to prevent directory traversal sequences from being processed in the plugin parameter. Organizations should also conduct regular security audits of their WordPress installations, ensure proper access controls are in place, and maintain up-to-date security monitoring systems to detect potential exploitation attempts. Additionally, implementing principle of least privilege access controls and regular credential rotation can help minimize the impact if an attacker gains administrative access to the system.