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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
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
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.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-89054 being exploited?
There is no known exploitation of CVE-2026-89054 in the wild and no public exploit code.
Sources
Also known as GHSA-hcpr-9cm8-436x.