CVE-2016-20010 in Image Optimizer
Summary
by MITRE • 05/05/2021
EWWW Image Optimizer before 2.8.5 allows remote command execution because it relies on a protection mechanism involving boolval, which is unavailable before PHP 5.5.
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Analysis
by VulDB Data Team • 05/07/2021
The EWWW Image Optimizer plugin for WordPress presents a critical remote command execution vulnerability identified as CVE-2016-20010 affecting versions prior to 285. This vulnerability stems from the plugin's reliance on a flawed security mechanism that depends on the boolval function, which was introduced in PHP 55 and is unavailable in earlier PHP versions. The flaw creates a dangerous condition where an attacker can execute arbitrary commands on the target system, potentially leading to complete compromise of the WordPress installation and underlying server infrastructure.
The technical implementation of this vulnerability involves the plugin's attempt to validate user input through a protection mechanism that assumes the existence of the boolval function. When the plugin operates on a server running PHP versions earlier than 55, this function does not exist, causing the validation logic to fail catastrophically. This failure allows malicious input to bypass intended security checks and directly influence the plugin's command execution paths. The vulnerability specifically affects the plugin's image optimization functionality where user-supplied parameters are processed without proper sanitization, creating a direct pathway for command injection attacks.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass complete system compromise capabilities. An attacker exploiting this vulnerability can execute arbitrary shell commands with the privileges of the web server process, potentially leading to data exfiltration, server takeover, or deployment of additional malicious tools. The vulnerability is particularly dangerous in shared hosting environments or multi-tenant WordPress installations where a single compromised plugin can affect multiple websites hosted on the same server. This weakness aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and represents a classic example of command injection vulnerability.
Security practitioners should prioritize immediate patching of affected systems to address this vulnerability, as the remediation involves updating the EWWW Image Optimizer plugin to version 285 or later. Additionally, administrators should implement proper input validation and sanitization measures at multiple layers, including web application firewalls and server-level restrictions. The vulnerability demonstrates the importance of avoiding deprecated PHP functions and ensuring backward compatibility in security mechanisms. Organizations should also consider implementing runtime monitoring to detect suspicious command execution patterns and establish robust patch management processes to prevent similar issues in the future. This vulnerability serves as a reminder of the critical importance of maintaining up-to-date software and understanding the PHP version requirements of security features in web applications.