OpenNMS Group Horizon/Meridian Web User Interface cross site scripting

Summaryinfo

A vulnerability categorized as problematic has been discovered in OpenNMS Group Horizon and Meridian. The affected element is an unknown function of the component Web User Interface. Executing a manipulation can lead to cross site scripting. This vulnerability is handled as CVE-2026-127235. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability has been found in OpenNMS Group Horizon and Meridian (affected version unknown) and classified as problematic. This vulnerability affects an unknown functionality of the component Web User Interface. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. CVE summarizes:

A reflected cross-site scripting vulnerability exists in the web user interface of multiple versions of OpenNMS Meridian and Horizon. Several web UI pages copy request parameter values into the HTML response without correct contextual output encoding. A remote attacker can craft a link that runs arbitrary JavaScript in the OpenNMS origin when an authenticated user opens it. The script runs in the victim's browser with the victim's session, so the attacker can read page data and send same-origin requests as the victim. The fix encodes the affected request values. On pages that use AngularJS, the fix also stops client-side template evaluation of the reflected values. The solution is to upgrade to Meridian 2024.3.15, 2025.0.12, 2026.0.2 and Horizon 36.0.6 or newer. Meridian and Horizon installation instructions state that they are intended for installation within an organization's private networks and should not be directly accessible from the Internet.

The advisory is available at github.com. This vulnerability was named CVE-2026-127235 since 11/12/2026. The exploitation appears to be easy. The attack can be initiated remotely. Successful exploitation requires user interaction by the victim. The technical details are unknown and an exploit is not available. This vulnerability is assigned to T1059.007 by the MITRE ATT&CK project.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• OpenNMS Group

Name

• Horizon
• Meridian

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