OpenNMS Group Horizon up to 36.0.3 REST API /api/v2 improper authorization

Summaryinfo

A vulnerability was found in OpenNMS Group Horizon up to 36.0.3 and classified as critical. The affected element is an unknown function of the file /api/v2 of the component REST API. The manipulation results in improper authorization. This vulnerability is known as CVE-2026-89054. It is possible to launch the attack remotely. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in OpenNMS Group Horizon up to 36.0.3. Affected is an unknown code of the file /api/v2 of the component REST API. The manipulation with an unknown input leads to a improper authorization vulnerability. CWE is classifying the issue as CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. This is going to have an impact on integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-89054 since 09/10/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1548.002 by the MITRE ATT&CK project.

Upgrading to version 36.0.4 eliminates this vulnerability.

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Productinfo

Vendor

• OpenNMS Group

Name

• Horizon

Version

• 36.0.0
• 36.0.1
• 36.0.2
• 36.0.3

CPE 2.3info

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CPE 2.2info

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