Is CVE-2026-127235 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-127235 being exploited in the wild.

How severe is CVE-2026-127235?

Medium severity, with a CVSS score of 6.1, published 12 November 2026.

Which products and versions are affected?

OpenNMS Horizon before 36.0.6; OpenNMS Meridian before 2024.3.15, 2025.0.12, 2026.0.2.

How is CVE-2026-127235 attacked?

It is attacked over the network, in a web application.

Am I affected by CVE-2026-127235?

Check whether you run OpenNMS Horizon or OpenNMS Meridian at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-127235: OpenNMS Meridian and Horizon reflected cross-site scripting in web UI

CVE-2026-127235 · Severity: medium · CVSS 6.1 · Published 2026-11-12

OpenNMS Meridian and Horizon are network monitoring and management platforms deployed within enterprise networks. A reflected cross-site scripting vulnerability in their web user interface allows an attacker to craft a malicious link that executes arbitrary JavaScript in an authenticated user's browser session. An attacker could steal sensitive monitoring data or perform administrative actions impersonating the victim.

Technologies: OpenNMS Horizon, OpenNMS Meridian. Vendors: OpenNMS.

Quick answers

Is CVE-2026-127235 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-127235 being exploited in the wild.
How severe is CVE-2026-127235?: Medium severity, with a CVSS score of 6.1, published 12 November 2026.
Which products and versions are affected?: OpenNMS Horizon before 36.0.6; OpenNMS Meridian before 2024.3.15, 2025.0.12, 2026.0.2.
Is there a fix for CVE-2026-127235?: Yes: fixed in Meridian 2024.3.15, 2025.0.12, 2026.0.2; Horizon 36.0.6. Until then: Ensure OpenNMS Meridian and Horizon installations are restricted to private network access and not directly accessible from the internet, as stated in vendor installation guidance. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-127235 attacked?: It is attacked over the network, in a web application.
Am I affected by CVE-2026-127235?: Check whether you run OpenNMS Horizon or OpenNMS Meridian at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: Meridian 2024.3.15, 2025.0.12, 2026.0.2; Horizon 36.0.6

Ensure OpenNMS Meridian and Horizon installations are restricted to private network access and not directly accessible from the internet, as stated in vendor installation guidance.

Technical details

Multiple web UI pages in OpenNMS Meridian and Horizon copy request parameter values into HTML responses without proper contextual output encoding. A remote, unauthenticated attacker can craft a link containing JavaScript payload that executes when an authenticated user visits it; the script runs in the victim's browser with their session privileges, allowing data exfiltration and same-origin requests. The fix applies context-specific HTML and JavaScript escaping across affected pages and disables client-side template evaluation for reflected values in AngularJS components.

Affected products

OpenNMS Meridian before 2024.3.15, 2025.0.12, 2026.0.2
OpenNMS Horizon before 36.0.6

Timeline

2026-11-12: disclosed

References

https://github.com/OpenNMS/opennms/pull/9066

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