Is CVE-2026-89054 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-89054 being exploited in the wild.

How severe is CVE-2026-89054?

High severity, with a CVSS score of 8.2, published 10 September 2026.

Which products and versions are affected?

OpenNMS Horizon prior to 36.0.4.

Is there a fix for CVE-2026-89054?

A patch was published on 2026-09: Fix merged in Horizon 36.0.4 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-89054 attacked?

It is attacked over the network, in a network appliance.

Am I affected by CVE-2026-89054?

Check whether anything you run is named in the advisory. 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-2026-89054: OpenNMS Horizon authorization bypass in /api/v2 PATCH endpoints

CVE-2026-89054 · Severity: high · CVSS 8.2 · Published 2026-09-10

OpenNMS Horizon is a network monitoring and alerting system used to track infrastructure health and generate alarms. An unauthenticated attacker who can reach the web interface can disable event definitions and SNMP data collection, silently suppressing alarms and stopping metric collection—degrading the organization's ability to detect and respond to network and system failures.

Quick answers

Is CVE-2026-89054 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-89054 being exploited in the wild.
How severe is CVE-2026-89054?: High severity, with a CVSS score of 8.2, published 10 September 2026.
Which products and versions are affected?: OpenNMS Horizon prior to 36.0.4.
Is there a fix for CVE-2026-89054?: A patch was published on 2026-09: Fix merged in Horizon 36.0.4 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-89054 attacked?: It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-89054?: Check whether anything you run is named in the advisory. 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.

Technical details

A missing authorization vulnerability exists in OpenNMS Horizon's Spring Security policy for the /api/v2 REST API. The security configuration defines authorization rules for all HTTP methods except PATCH, leaving PATCH endpoints for event configuration and SNMP data collection unprotected. An unauthenticated attacker with network access to the web UI can send PATCH requests to disable event definitions and data-collection sources, with changes persisted to the running system. The vulnerability requires network reachability to the web interface but no authentication. A patch is available in Horizon 36.0.4 and later.

Affected products

OpenNMS Horizon prior to 36.0.4

Timeline

2026-09-10: disclosed: CVE-2026-89054 published
2026-09: patched: Fix merged in Horizon 36.0.4

References

https://github.com/OpenNMS/opennms/pull/8833

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