CVE-2016-6556 in OpenNMS
Summary
by MITRE • 09/25/2021
OpenNMS version 18.0.1 and prior are vulnerable to a stored XSS issue due to insufficient filtering of SNMP agent supplied data. By creating a malicious SNMP 'sysName' or 'sysContact' response, an attacker can store an XSS payload which will trigger when a user of the web UI views the data. This issue was fixed in version 18.0.2, released on September 20, 2016.
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Analysis
by VulDB Data Team • 10/02/2021
The vulnerability identified as CVE-2016-6556 represents a critical stored cross-site scripting flaw in OpenNMS versions 18.0.1 and earlier, demonstrating a fundamental weakness in input validation and output sanitization within network monitoring systems. This issue arises from the improper handling of SNMP agent supplied data, specifically targeting the sysName and sysContact SNMP object values that are commonly used to identify network devices and their administrative contacts. The vulnerability exists because the OpenNMS platform fails to adequately filter or escape user-supplied data before storing it in its database and subsequently rendering it in the web user interface without proper context-aware escaping mechanisms.
The technical exploitation of this vulnerability occurs through manipulation of SNMP responses, where an attacker crafts malicious SNMP sysName or sysContact values containing XSS payloads that get stored within the OpenNMS database. When legitimate users access the web interface to view device information, these stored payloads execute in the context of the victim's browser session, potentially leading to session hijacking, credential theft, or unauthorized administrative actions. The vulnerability is classified as a stored XSS attack because the malicious code is permanently stored on the server and executed whenever the affected data is retrieved and displayed, rather than requiring immediate interaction with a vulnerable page.
From an operational perspective, this vulnerability presents a significant risk to network monitoring environments that rely on OpenNMS for device management and system oversight. Network administrators who frequently view device information through the web interface become potential victims of this attack, as the XSS payload could execute with the privileges of the logged-in user, potentially escalating to full administrative control of the monitoring system. The attack vector is particularly concerning because it leverages legitimate SNMP communication protocols, making it difficult to detect through traditional network monitoring tools that might not flag the malicious SNMP responses as suspicious traffic. This vulnerability directly aligns with CWE-79, which describes cross-site scripting flaws, and represents a classic case of insufficient input validation and output encoding in web applications.
The remediation for this vulnerability required the implementation of proper input sanitization and output escaping mechanisms within OpenNMS version 18.0.2, which was released on September 20, 2016. The fix involved ensuring that all SNMP-supplied data is properly escaped and validated before being stored in the database and rendered in the web interface. Organizations should implement immediate patching of affected systems and consider additional security measures such as network segmentation, monitoring for suspicious SNMP traffic patterns, and implementing web application firewalls to detect and prevent exploitation attempts. The vulnerability also highlights the importance of applying security patches promptly, as it remained unpatched for several months after the initial disclosure, providing attackers with ample time to develop and deploy exploitation tools. This case study serves as a reminder of the critical importance of input validation in network management systems, particularly those handling data from potentially untrusted sources such as SNMP agents, and demonstrates how vulnerabilities in monitoring infrastructure can have far-reaching consequences for overall network security posture.