CVE-2026-89054 is a high-severity (CVSS 8.2) CWE-862 vulnerability. O3 Security confirms whether CVE-2026-89054 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
A missing authorization vulnerability in OpenNMS Horizon allows configuration changes without authentication. The Spring Security policy for the /api/v2 REST API defines authorization…
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-89054.
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.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-89054 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-89054 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-89054. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-89054 in your dependencies?
O3 detects CVE-2026-89054 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.