CVE-2026-19182 Missing authorization in Horizon
Low-privileged users can bypass authorization checks to modify alarm states and impersonate other users in OpenNMS network monitoring systems.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-19182?
CVE-2026-19182 is a medium-severity missing authorization vulnerability in The OpenNMS Group Horizon, published on 13 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
An incorrect authorization check in the v2 Alarm REST API in OpenNMS Meridian and Horizon allows a low-privileged authenticated user (ROLE_REST) to acknowledge, escalate, or clear alarms recorded as an arbitrary username, and, when also assigned ROLE_READONLY, to modify alarm state despite the read-only restriction. A credential check that should restrict these operations is guarded by an inverted condition, so it never executes for a real (non-blank) username. This can potentially allow an attacker to compromise the integrity of alarm state and audit records.
The solution is to upgrade to Meridian 2024.3.12, 2025.0.9 and Horizon 36.0.3 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-863
Which versions are affected by CVE-2026-19182?
How do I fix CVE-2026-19182?
No fix has been published for CVE-2026-19182 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-2026-19182 being exploited?
There is no known exploitation of CVE-2026-19182 in the wild and no public exploit code.
Sources
Also known as GHSA-r53w-fffc-9ppv.