CVE-2016-2056 in Xymon
Summary
by MITRE
xymond in Xymon 4.1.x, 4.2.x, and 4.3.x before 4.3.25 allow remote authenticated users to execute arbitrary commands via shell metacharacters in the adduser_name argument in (1) web/useradm.c or (2) web/chpasswd.c.
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Analysis
by VulDB Data Team • 01/20/2025
The vulnerability CVE-2016-2056 represents a critical command injection flaw in Xymon monitoring software versions 4.1.x through 4.3.24, affecting the web-based user administration components. This security weakness resides in the handling of user input within the adduser_name argument, specifically within the web/useradm.c and web/chpasswd.c modules of the Xymon application. The vulnerability enables authenticated remote attackers to execute arbitrary commands on the affected system by leveraging shell metacharacters within the targeted parameter.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within the user administration functions. When the system processes user requests to add new users or change passwords through the web interface, it fails to properly escape or filter special shell characters such as semicolons, ampersands, backticks, and pipes. This inadequate sanitization allows attackers who have authenticated access to the system to inject malicious shell commands that get executed with the privileges of the web application process. The flaw operates at the application layer and specifically targets the command execution mechanisms used by Xymon for user management operations.
The operational impact of this vulnerability is severe and multifaceted, as it provides attackers with elevated privileges and persistent access to the monitoring infrastructure. Since the vulnerability requires only authenticated access, it can be exploited by malicious insiders or compromised legitimate users with appropriate permissions. Successful exploitation allows attackers to execute arbitrary code on the server, potentially leading to full system compromise, data exfiltration, or disruption of monitoring services. The affected Xymon installations may contain sensitive network monitoring data and system information, making them attractive targets for adversaries seeking to escalate privileges or establish persistent backdoors.
From a cybersecurity framework perspective, this vulnerability maps to CWE-78, which describes improper neutralization of special elements used in OS commands, and aligns with ATT&CK technique T1059.001 for command and script injection. The vulnerability also demonstrates characteristics of privilege escalation and persistence mechanisms, potentially correlating with ATT&CK techniques T1068 for exploit for privilege escalation and T1543.003 for create or modify system process. Organizations should implement immediate mitigations including upgrading to Xymon version 4.3.25 or later, which contains the necessary input validation patches. Additional protective measures include implementing network segmentation, restricting web-based administrative access, enabling strict input validation, and monitoring for suspicious command execution patterns. Regular security assessments and vulnerability scanning should be conducted to identify similar injection vulnerabilities in other components of the monitoring infrastructure.