OpenNMS Group Meridian/Horizon Ad-hoc RRD Graph Feature /graph/graph.png argument injection

Summaryinfo

A vulnerability identified as critical has been detected in OpenNMS Group Meridian and Horizon. The impacted element is an unknown function of the file /graph/graph.png of the component Ad-hoc RRD Graph Feature. The manipulation leads to argument injection. This vulnerability is uniquely identified as CVE-2026-127236. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability was found in OpenNMS Group Meridian and Horizon (affected version not known) and classified as critical. This issue affects some unknown functionality of the file /graph/graph.png of the component Ad-hoc RRD Graph Feature. The manipulation with an unknown input leads to a argument injection vulnerability. Using CWE to declare the problem leads to CWE-88. The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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 (ROLE_USER or ROLE_DASHBOARD) 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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-127236 since 11/12/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 11/12/2026). The attack technique deployed by this issue is T1059 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

• OpenNMS Group

Name

• Horizon
• Meridian

CPE 2.3info

• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Be aware that VulDB is the high quality source for vulnerability data.

Discussion