CVE-2026-127236: OpenNMS argument injection in ad-hoc RRD graphs
An argument injection vulnerability exists in the ad-hoc RRD graph feature of multiple versions of OpenNMS Meridian and Horizon. The ad-hoc graph endpoint (GET /graph/graph.png?adhoc=true) copies request parameters into the rrdtool command line without validation. A low-privileged authenticated user (ROLEUSER or ROLEDASHBOARD) can insert extra rrdtool arguments. An injected --daemon argument makes the server connect to an attacker-chosen address, which is a server-side request forgery. An injected DEF statement reads a local RRD file by absolute path. The command runs through exec with an argument array and no shell, so arbitrary operating system command execution is not possible. The fix validates the ad-hoc graph parameters against allowlists.
The solution is to upgrade to Meridian 2024.3.15, 2025.0.12, 2026.0.2 and Horizon 36.0.6 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.
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
OpenNMS Meridianto a version that resolves this vulnerability.Fixed in 2024.3.15 - Upgrade
Upgrade
OpenNMS Meridianto a version that resolves this vulnerability.Fixed in 2025.0.12 - Upgrade
Upgrade
OpenNMS Meridianto a version that resolves this vulnerability.Fixed in 2026.0.2 - Upgrade
Upgrade
OpenNMS Horizonto a version that resolves this vulnerability.Fixed in 36.0.6
Event History
Frequently Asked Questions
Who can exploit this issue?
An authenticated user with either ROLE_USER or ROLE_DASHBOARD can exploit it. The affected functionality is the ad-hoc graph endpoint at GET /graph/graph.png?adhoc=true.
What can an attacker do with injected arguments?
An attacker can inject an rrdtool --daemon argument to make the server connect to an attacker-chosen address, creating an SSRF condition. They can also inject a DEF statement to read a local RRD file using an absolute path.
Does this allow arbitrary command execution on the OpenNMS server?
No. The rrdtool command is executed using an argument array without a shell, so arbitrary operating system command execution is not possible.
Which versions contain the fix?
Upgrade Meridian to 2024.3.15, 2025.0.12, or 2026.0.2 or newer, or upgrade Horizon to 36.0.6 or newer.
What should be done if an upgrade cannot be applied immediately?
Limit access to the OpenNMS instance and the ad-hoc graph endpoint to trusted authenticated users. OpenNMS Meridian and Horizon are intended for private-network deployment and should not be directly accessible from the Internet.