In OpenNMS Horizon, versions opennms-1-0-stable through opennms-27.1.0-1; OpenNMS Meridian, versions meridian-foundation-2015.1.0-1 through meridian-foundation-2019.1.18-1; meridian-foundation-2020.1.0-1 through meridian-foundation-2020.1.6-1 are vulnerable to Stored Cross-Site Scripting, since the function `validateFormInput()` performs improper validation checks on the input sent to the `userID` parameter. Due to this flaw an attacker could inject an arbitrary script which will be stored in the database.

OpenNMS is accessible via port 9443

An issue was discovered in OpenNMS Horizon before 26.0.1, and Meridian before 2018.1.19 and 2019 before 2019.1.7. The ActiveMQ channel configuration allowed for arbitrary deserialization of Java objects (aka ActiveMQ Minion payload deserialization), leading to remote code execution for any authenticated channel user regardless of its assigned permissions.

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.

OpenNMS version 18.0.1 and prior are vulnerable to a stored XSS issue due to insufficient filtering of SNMP trap supplied data. By creating a malicious SNMP trap, an attacker can store an XSS payload which will trigger when a user of the web UI views the events list page. This issue was fixed in version 18.0.2, released on September 20, 2016.

OpenNMS has a default password of rtc for the rtc account, which makes it easier for remote attackers to obtain access by leveraging knowledge of the credentials.

Multiple cross-site scripting (XSS) vulnerabilities in OpenNMS before 1.12.7 allow remote attackers to inject arbitrary web script or HTML via unspecified vectors.

Cross-site scripting (XSS) vulnerability in web/springframework/security/SecurityAuthenticationEventOnmsEventBuilder.java in OpenNMS 1.8.x before 1.8.17, 1.9.93 and earlier, and 1.10.x before 1.10.1 allows remote attackers to inject arbitrary web script or HTML via the Username field, related to login.

Cross-site scripting (XSS) vulnerability in surveillanceView.htm in OpenNMS 1.5.94 allows remote attackers to inject arbitrary web script or HTML via the viewName parameter.

Multiple cross-site scripting (XSS) vulnerabilities in OpenNMS before 1.5.94 allow remote attackers to inject arbitrary web script or HTML via (1) the j_username parameter to j_acegi_security_check, (2) the username parameter to notification/list.jsp, and (3) the filter parameter to event/list.