Vulnerability · Published Sep 10, 2026 · Assigned by OpenNMS
CVE-2026-89054OpenNMS missing authorization on /api/v2 PATCH endpoints allows unauthenticated configuration changes
High 8.2
In plain English
A high-severity missing authorization in Horizon from The OpenNMS Group. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities).
Official description
A missing authorization vulnerability in OpenNMS Horizon allows configuration changes without authentication. The Spring Security policy for the /api/v2 REST API defines authorization rules for every HTTP method except PATCH, so the shipped @PATCH configuration endpoints for event configuration and SNMP data collection (which enable and disable event definitions and data-collection sources) are reachable with no authorization enforced. An unauthenticated attacker able to reach the web UI can disable event definitions and SNMP data collection, suppressing event and alarm generation and stopping metric collection - silently degrading monitoring and detection - with the change persisted and reloaded into the running system. The solution is to upgrade to Horizon 36.0.4 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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| The OpenNMS Group | Horizon | 36.0.0 – before 36.0.4 |
Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L