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.
Published: 2026-09-10
Score: 5.9 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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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

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History

Thu, 10 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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


Thu, 10 Sep 2026 20:30:00 +0000

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'}


Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: OpenNMS

Published:

Updated: 2026-09-10T20:27:45.533Z

Reserved: 2026-08-12T06:24:26.987Z

Link: CVE-2026-19596

cve-icon Vulnrichment

Updated: 2026-09-10T20:27:42.851Z

cve-icon NVD

Status : Received

Published: 2026-09-10T21:17:25.667

Modified: 2026-09-10T21:17:25.667

Link: CVE-2026-19596

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-10T22:30:08Z

Weaknesses
  • CWE-611

    Improper Restriction of XML External Entity Reference