CVE-2026-19182

OpenNMS v2 Alarm REST API inverted authorization check lets ROLE_REST users acknowledge alarms as any user and bypass read-only

Published Aug 13, 2026 CVSS 3.1 · 4.3 Medium EPSS < 1% KEV · Not listed
Description
An incorrect authorization check in the v2 Alarm REST API in OpenNMS Meridian and Horizon allows a low-privileged authenticated user (ROLE_REST) to acknowledge, escalate, or clear alarms recorded as an arbitrary username, and, when also assigned ROLE_READONLY, to modify alarm state despite the read-only restriction. A credential check that should restrict these operations is guarded by an inverted condition, so it never executes for a real (non-blank) username. This can potentially allow an attacker to compromise the integrity of alarm state and audit records.



The solution is to upgrade to Meridian 2024.3.12, 2025.0.9 and Horizon 36.0.3 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.

Remediation

Vendor Solution

Upgrade to Meridian 2024.3.12, 2025.0.9 and Horizon 36.0.3 or newer.

Tracking

Sign in to view the affected projects.

Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Opennms
Opennms horizon
Opennms meridian
Vendors & Products Opennms
Opennms horizon
Opennms meridian
Type Values Removed Values Added
Description An incorrect authorization check in the v2 Alarm REST API in OpenNMS Meridian and Horizon allows a low-privileged authenticated user (ROLE_REST) to acknowledge, escalate, or clear alarms recorded as an arbitrary username, and, when also assigned ROLE_READONLY, to modify alarm state despite the read-only restriction. A credential check that should restrict these operations is guarded by an inverted condition, so it never executes for a real (non-blank) username. This can potentially allow an attacker to compromise the integrity of alarm state and audit records. The solution is to upgrade to Meridian 2024.3.12, 2025.0.9 and Horizon 36.0.3 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.
Title OpenNMS v2 Alarm REST API inverted authorization check lets ROLE_REST users acknowledge alarms as any user and bypass read-only
Weaknesses CWE-863
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
OpenNMS
Published
Updated
Aug 13, 2026, 1:01 PM
Reserved
Aug 6, 2026, 6:03 PM
Status
Awaiting Analysis
Published
Aug 13, 2026, 5:17 AM
Modified
Sep 8, 2026, 7:20 PM