---
id: CVE-2026-111252
title: >-
  A denial of service vulnerability exists in the XML parsing of multiple
  versions of OpenNMS Meridian and Horizon
summary: >-
  A denial of service vulnerability exists in the XML parsing of multiple
  versions of OpenNMS Meridian and Horizon. OpenNMS parsed XML without an
  effective limit on entity expansion. A document with a DOCTYPE that declares
  internal entitie…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-400
  - CWE-776
vendor: The OpenNMS Group
product: Meridian
affected:
  - Meridian >= 2024.1.0 < 2024.3.14
  - Meridian >= 2025.0.0 < 2025.0.11
  - Meridian >= 2026.0.0 < 2026.0.1
  - Horizon >= 36.0.0 < 36.0.5
published: '2026-10-15'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T19:17:36.827'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-111252'
references:
  - url: 'https://github.com/OpenNMS/opennms/pull/8898'
    label: security@opennms.com
  - url: 'https://github.com/OpenNMS/opennms/pull/8952'
    label: security@opennms.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-10-15T19:25:46.433Z'
---

## Overview

A denial of service vulnerability exists in the XML parsing of multiple versions of OpenNMS Meridian and Horizon. OpenNMS parsed XML without an effective limit on entity expansion. A document with a DOCTYPE that declares internal entities can expand to a very large value and exhaust the server memory. An authenticated user with provisioning access can supply such a document through a requisition or foreign-source import, which includes a remote requisition URL that the server fetches and parses. Both deeply nested entities and a single large entity referenced many times cause the memory exhaustion. The fix caps the number of entity expansions for all XML parsing and rejects any DOCTYPE in requisition and foreign-source XML.



The solution is to upgrade to Meridian 2024.3.14, 2025.0.11, 2026.0.1 and Horizon 36.0.5 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

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.