CVE-2026-19596
MEDIUMDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 12% of all known CVEs.
References
Related Vulnerabilities
Other CWE-611 (XML External Entity (XXE)) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2024-34102 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2019-9670 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2022-28219 | Critical | 9.8 | 97% | - | - |
| CVE-2024-22024 | High | 8.3 | 95% | - | - |
| CVE-2024-38653 | High | 7.5 | 92% | - | - |
| CVE-2017-12629 | Critical | 9.8 | 92% | - | Fix |
Common questions
How do I fix CVE-2026-19596?
No published fix for CVE-2026-19596 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-19596 being actively exploited?
Not that we know of. CVE-2026-19596 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.21% is the estimated probability that it will be exploited in the next 30 days. That is higher than 12% of all scored CVEs.
How severe is CVE-2026-19596?
CVE-2026-19596 has a CVSS v3 base score of 5.9, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-09-18.