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TI-2026-74979 Aliases CVE-2026-111252

Denial of service in OpenNMS Meridian and Horizon via XML entities

Priority LOW 28CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-400.

Summary

OpenNMS Meridian from 2024.1.0 before 2024.3.14, from 2025.0.0 before 2025.0.11, from 2026.0.0 before 2026.0.1, and Horizon from 36.0.0 before 36.0.5, parse XML without an effective limit on entity expansion (CWE-776). An authenticated user with provisioning access can import a requisition or foreign-source document with a DOCTYPE declaring internal entities that expand to huge sizes. This exhausts server memory and causes denial of service.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00249 16th percentileScored 2026-11-07
Fix Fixed Meridian (The OpenNMS Group): 2024.3.14, 2025.0.11, 2026.0.1Horizon (The OpenNMS Group): 36.0.5

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
The OpenNMS GroupMeridian2024.1.0 to before 2024.3.14; 2025.0.0 to before 2025.0.11; 2026.0.0 to before 2026.0.12024.3.14, 2025.0.11, 2026.0.1Patch availableCNA
The OpenNMS GroupHorizon36.0.0 to before 36.0.536.0.5Patch availableCNA
  • Meridian VendorThe OpenNMS Group Affected 2024.1.0 to before 2024.3.14; 2025.0.0 to before 2025.0.11; 2026.0.0 to before 2026.0.1 Fixed in 2024.3.14, 2025.0.11, 2026.0.1 Patch available CNA
  • Horizon VendorThe OpenNMS Group Affected 36.0.0 to before 36.0.5 Fixed in 36.0.5 Patch available CNA

Remediation

Upgrade Meridian to 2024.3.14, 2025.0.11 or 2026.0.1, or Horizon to 36.0.5 or newer. The vendor's installation instructions state that Meridian and Horizon should be kept within private networks and not be directly accessible from the Internet.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

  • Fix · CNA Meridian (The OpenNMS Group) Fixed in 2024.3.14, 2025.0.11, 2026.0.1
  • Fix · CNA Horizon (The OpenNMS Group) Fixed in 36.0.5

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    The OpenNMS Group Horizon, Meridian 2024.3.14, 2025.0.11 and 2 more versions

    2 records Highest priority Priority MEDIUM 1 MEDIUM, 1 LOW

    Other records, highest priority first

    • TI-2026-74978 OpenNMS REST authorization bypass via non-canonical HTTP methodPriority MEDIUM 47
    Show all 2 records →

Timeline

  1. 2026-10-16 Threatist record created from CVE-2026-111252
  2. 2026-10-16 Priority changed: MEDIUM → LOW
  3. 2026-10-18 CISA SSVC decision points changed

References

Patch 2

  • TI-2021-07941 Cross-site request forgery in OpenNMS CVSS 3.1HIGH 8.8
  • TI-2021-07943 Cross-site scripting in OpenNMS CVSS 3.1MEDIUM 4.8
  • TI-2021-07939 Cross-site scripting in OpenNMS CVSS 3.1MEDIUM 4.8
  • TI-2021-07940 Cross-site request forgery in OpenNMS CVSS 3.1MEDIUM 4.3
  • TI-2015-06530 OpenNMS has a default password of rtc for the rtc account, which makes it easier for… CVSS 2.0HIGH 10.0
  • TI-2026-74978 OpenNMS REST authorization bypass via non-canonical HTTP method CVSS 3.1CRITICAL 9.1
See all 38 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences