Skip to content
Fencer Intel
medium 5.4

CVE-2026-127236 json

OpenNMS argument injection in ad-hoc RRD graphs

published 2d ago modified 2d ago also EUVD-2026-124611

cvss
5.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 31%
public exploits
0
none known

Summary

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.

Patch / fix

  • The OpenNMS Group Meridian 2024.3.15, 2025.0.12, 2026.0.2
  • The OpenNMS Group Horizon 36.0.6

Is CVE-2026-127236 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Exploit prediction

0.37% chance of exploitation in the next 30 days, higher than 31% of all scored CVEs (FIRST EPSS, 2026-11-14).

CVSS scores

assigned by version score vector
CNA 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Affected products

  • The OpenNMS Group Meridian
  • The OpenNMS Group Horizon

Classification

Weakness
  • CWE-88 Improper Neutralization of Argument Delimiters in a Command

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.