# CVE-2026-89054: OpenNMS missing authorization on /api/v2 PATCH endpoints allows unauthenticated configuration changes

> Unauthenticated attackers can modify event and SNMP configurations in OpenNMS Horizon, disabling monitoring and alarm generation.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Sep 2026
- **Updated:** 10 Sep 2026
- **Also known as:** GHSA-hcpr-9cm8-436x

## What is CVE-2026-89054?

CVE-2026-89054 is a high-severity missing authorization vulnerability in The OpenNMS Group Horizon, published on 10 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-89054?


## How do I fix CVE-2026-89054?

No fix has been published for CVE-2026-89054 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-89054 being exploited?

There is no known exploitation of CVE-2026-89054 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89054 and fix it if it is affected.

What it is: CVE-2026-89054 is a high-severity missing authorization vulnerability in The OpenNMS Group Horizon, published on 10 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89054 in the wild and no public exploit code.

Affected product: The OpenNMS Group Horizon. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-89054/ (Markdown: https://insights.sbomify.com/CVE-2026-89054/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89054
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89054
- OSV: https://osv.dev/vulnerability/CVE-2026-89054

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89054/
Summaries are generated and may contain mistakes; the official description above is the record.