CVE-2016-4338 in Zabbix
Summary
by MITRE
The mysql user parameter configuration script (userparameter_mysql.conf) in the agent in Zabbix before 2.0.18, 2.2.x before 2.2.13, and 3.0.x before 3.0.3, when used with a shell other than bash, allows context-dependent attackers to execute arbitrary code or SQL commands via the mysql.size parameter.
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability described in CVE-2016-4338 represents a critical security flaw in the Zabbix monitoring system's MySQL user parameter configuration script. This issue affects multiple versions of the Zabbix agent including 2.0.17 and earlier, 2.2.12 and earlier, and 3.0.2 and earlier releases. The vulnerability stems from improper handling of user input within the mysql.size parameter when the system shell is not bash, creating a dangerous execution context that can be exploited by malicious actors. The flaw specifically manifests in how the agent processes the mysql.size parameter, which is designed to retrieve MySQL database size information through user-defined parameters.
The technical implementation of this vulnerability relies on shell command injection techniques that exploit the difference in how various shells handle parameter expansion and command execution. When the Zabbix agent processes the mysql.size parameter with non-bash shells such as sh, dash, or other POSIX-compliant shells, the input validation fails to properly sanitize user-provided data. This results in arbitrary command execution capabilities where attackers can inject malicious commands that get executed within the context of the Zabbix agent process. The vulnerability is context-dependent because it requires specific environmental conditions, particularly the use of non-bash shells, to be exploitable. This aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and demonstrates how shell injection flaws can be weaponized in monitoring systems.
The operational impact of this vulnerability is severe as it allows attackers to execute arbitrary code with the privileges of the Zabbix agent process, potentially leading to full system compromise. An attacker who gains access to the Zabbix monitoring infrastructure can leverage this vulnerability to perform SQL injection attacks against MySQL databases, execute system commands, and escalate privileges within the monitored environment. The attack vector typically involves crafting malicious input for the mysql.size parameter that gets processed through shell commands, enabling unauthorized access to sensitive data and system resources. This vulnerability particularly affects organizations that rely heavily on Zabbix for infrastructure monitoring, as the compromised agent can provide attackers with persistent access to monitored systems and databases. The implications extend beyond simple code execution to include potential data exfiltration, lateral movement within networks, and establishment of persistent backdoors through the compromised monitoring infrastructure.
Mitigation strategies for CVE-2016-4338 should focus on immediate version upgrades to patched releases of Zabbix, specifically versions 2.0.18, 2.2.13, and 3.0.3 or later. Organizations should also implement proper input validation and sanitization within their Zabbix configurations, particularly for user parameters that interact with shell commands. Network segmentation and access controls should be strengthened to limit exposure of Zabbix agents to untrusted networks. The implementation of principle of least privilege for Zabbix agent processes and database connections can significantly reduce the impact of successful exploitation. Additionally, organizations should consider implementing monitoring for unusual command execution patterns and parameter usage that might indicate exploitation attempts. Regular security audits of monitoring system configurations and shell command usage should be conducted to identify and remediate similar vulnerabilities. This vulnerability demonstrates the importance of secure coding practices in monitoring systems and aligns with ATT&CK techniques related to command and scripting interpreter execution and privilege escalation through system monitoring tools.