Auth bypass in The Opennms Group Horizon
CVE-2026-19182
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.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (15.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 15.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
- The Opennms Group Horizon — versions 36.0.0
- The Opennms Group Meridian — versions 2024.1.0, 2025.0.0
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-19182?
- CVE-2026-19182 is a medium-severity vulnerability in The Opennms Group Horizon, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2026-08-13.
- How severe is CVE-2026-19182?
- Medium severity. CVSS v3 base score is 4.3 out of 10.