CVE-2026-19182: CWE-863 Incorrect Authorization in The OpenNMS Group Meridian
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.
AI Analysis
Technical Summary
This vulnerability (CVE-2026-19182) in OpenNMS Meridian and Horizon arises from an incorrect authorization check in the v2 Alarm REST API. A low-privileged authenticated user with ROLE_REST can perform alarm state changes (acknowledge, escalate, clear) under arbitrary usernames. When combined with ROLE_READONLY, the user can modify alarm states despite supposed read-only restrictions. The root cause is an inverted condition in the credential check that prevents proper enforcement for non-blank usernames. This flaw can undermine the integrity of alarm states and audit trails. The vulnerability affects Meridian versions 2024.1.0 and 2025.0.0 and Horizon 36.0.0, specifically versions before Meridian 2024.3.12 and 2025.0.9, and Horizon 36.0.3. The vendor advises upgrading to these versions to remediate the issue. The products are designed for private network deployment and should not be exposed to the Internet.
Potential Impact
The vulnerability allows unauthorized modification of alarm states and audit records by low-privileged authenticated users, potentially compromising the integrity of alarm management and audit data. There is no impact on confidentiality or availability reported. The CVSS score is 4.3 (medium severity), reflecting limited impact confined to integrity with no elevation of privileges or denial of service.
Mitigation Recommendations
A fix is available by upgrading to Meridian 2024.3.12, 2025.0.9, or Horizon 36.0.3 or newer. Organizations should apply these updates promptly. Additionally, since these products are intended for private network use, ensure they are not directly accessible from the Internet to reduce exposure risk.
CVE-2026-19182: CWE-863 Incorrect Authorization in The OpenNMS Group Meridian
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.
CVSS v3.1
Score 4.3medium
Affected software
The OpenNMS Group
Meridian
The OpenNMS Group
Horizon
pkg:github/MeridianRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CVE-2026-19182) in OpenNMS Meridian and Horizon arises from an incorrect authorization check in the v2 Alarm REST API. A low-privileged authenticated user with ROLE_REST can perform alarm state changes (acknowledge, escalate, clear) under arbitrary usernames. When combined with ROLE_READONLY, the user can modify alarm states despite supposed read-only restrictions. The root cause is an inverted condition in the credential check that prevents proper enforcement for non-blank usernames. This flaw can undermine the integrity of alarm states and audit trails. The vulnerability affects Meridian versions 2024.1.0 and 2025.0.0 and Horizon 36.0.0, specifically versions before Meridian 2024.3.12 and 2025.0.9, and Horizon 36.0.3. The vendor advises upgrading to these versions to remediate the issue. The products are designed for private network deployment and should not be exposed to the Internet.
Potential Impact
The vulnerability allows unauthorized modification of alarm states and audit records by low-privileged authenticated users, potentially compromising the integrity of alarm management and audit data. There is no impact on confidentiality or availability reported. The CVSS score is 4.3 (medium severity), reflecting limited impact confined to integrity with no elevation of privileges or denial of service.
Mitigation Recommendations
A fix is available by upgrading to Meridian 2024.3.12, 2025.0.9, or Horizon 36.0.3 or newer. Organizations should apply these updates promptly. Additionally, since these products are intended for private network use, ensure they are not directly accessible from the Internet to reduce exposure risk.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- OpenNMS
- Date Reserved
- 2026-08-06T18:03:49.526Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a7d520ebf8831d539b45588
Added to database: 08/13/2026, 05:11:42 UTC
Last enriched: 08/13/2026, 05:30:08 UTC
Last updated: 09/25/2026, 19:43:24 UTC
Views: 66
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