CVE-2026-19596

OpenNMS XML collector XXE allows arbitrary file read from the OpenNMS host

Published Sep 10, 2026 CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed
Description
An XML External Entity (XXE) vulnerability exists in the XML collector of multiple versions of OpenNMS Meridian and Horizon. When OpenNMS collects XML from a source whose response is attacker-controlled (for example a compromised monitored host or an HTTP man-in-the-middle position), the collector's XML parser resolves external entities and external DTDs. This allows an attacker to read files accessible to the OpenNMS service account, including database credentials, and to induce out-of-band requests.



The solution is to upgrade to Meridian 2024.3.13, 2025.0.10 and 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.

Remediation

Vendor Solution

Upgrade to Meridian 2024.3.13, 2025.0.10 and Horizon 36.0.4 or newer.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared The Opennms Group
The Opennms Group horizon
The Opennms Group meridian
Vendors & Products The Opennms Group
The Opennms Group horizon
The Opennms Group meridian
Type Values Removed Values Added
Metrics ssvc

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

Type Values Removed Values Added
Description An XML External Entity (XXE) vulnerability exists in the XML collector of multiple versions of OpenNMS Meridian and Horizon. When OpenNMS collects XML from a source whose response is attacker-controlled (for example a compromised monitored host or an HTTP man-in-the-middle position), the collector's XML parser resolves external entities and external DTDs. This allows an attacker to read files accessible to the OpenNMS service account, including database credentials, and to induce out-of-band requests. The solution is to upgrade to Meridian 2024.3.13, 2025.0.10 and 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.
Title OpenNMS XML collector XXE allows arbitrary file read from the OpenNMS host
Weaknesses CWE-611
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
OpenNMS
Published
Updated
Sep 10, 2026, 8:27 PM
Reserved
Aug 12, 2026, 6:24 AM
Status
Awaiting Analysis
Published
Sep 10, 2026, 9:17 PM
Modified
Sep 18, 2026, 7:21 PM