OpenNMS missing authorization on /api/v2 PATCH endpoints allows unauthenticated configuration changes (CVE-2026-89054) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-89054

OpenNMS missing authorization on /api/v2 PATCH endpoints allows unauthenticated configuration changes

Answer in brief

CVE-2026-89054 records a Unknown severity vulnerability in OpenNMS missing authorization on /api/v2 PATCH endpoints allows unauthenticated configuration changes. The current sources do not mark it as known exploited. The current feed maps The OpenNMS Group/Horizon (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 10, 2026Updated Sep 10, 2026Source checked Sep 10, 2026First seen by HOL Sep 10, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps The OpenNMS Group/Horizon (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
The OpenNMS Group/Horizongeneric	>=36.0.0 <36.0.4	36.0.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for The OpenNMS Group/Horizon.
Review the reported fix. Update The OpenNMS Group/Horizon to 36.0.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 10, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 10, 2026

Sources and claim methodology

GitHub security advisorygithub.com

Upstream source description

A missing authorization vulnerability in OpenNMS Horizon allows configuration changes without authentication. The Spring Security policy for the /api/v2 REST API defines authorization rules for every HTTP method except PATCH, so the shipped @PATCH configuration endpoints for event configuration and SNMP data collection (which enable and disable event definitions and data-collection sources) are reachable with no authorization enforced. An unauthenticated attacker able to reach the web UI can disable event definitions and SNMP data collection, suppressing event and alarm generation and stopping metric collection - silently degrading monitoring and detection - with the change persisted and reloaded into the running system. The solution is to upgrade to 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.

Quoted source text, attributed separately from HOL analysis.