What’s Vulnerable › Vulnerabilities
CVE-2026-89054: OpenNMS missing authorization on /api/v2 PATCH endpoints allows unauthenticated configuration changes
- Severity: high (CVSS 8.2 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.5% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-09-10 · updated 2026-09-18
- Weakness: CWE-862
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
- The OpenNMS Group Horizon: from 36.0.0 before 36.0.4 — fixed in 36.0.4
How to fix
Upgrade to a fixed version: The OpenNMS Group Horizon 36.0.4. Check the vendor advisory for mitigations.
References
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