CVE-2026-19596 — OpenNMS XML collector XXE allows arbitrary file read from the OpenNMS host
An XML External Entity (XXE) vulnerability exists in the XML collector of multiple versions of OpenNMS Meridian and Horizon. When OpenNMS collects XML from a source whose respon…
Published: 2026-09-10 · CVSS: 5.9 · CVSS 3.1
An XML External Entity (XXE) vulnerability exists in the XML collector of multiple versions of OpenNMS Meridian and Horizon. When OpenNMS collects XML from a source whose response is attacker-controlled (for example a compromised monitored host or an HTTP man-in-the-middle position), the collector's XML parser resolves external entities and external DTDs. This allows an attacker to read files accessible to the OpenNMS service account, including database credentials, and to induce out-of-band requests. The solution is to upgrade to Meridian 2024.3.13, 2025.0.10 and 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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7