CVE-2026-19596: The OpenNMS Group Meridian · XML External Entity (XXE)
Affects The OpenNMS Group MeridianSource CVE Database V5
Not known to be exploited · CVSS 5.9 Medium : upgrade to 2025.0.10 or 2024.3.13 when convenient.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 26% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 2025.0.10, 2024.3.13, 36.0.4
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:NExploitation evidence
Disclosed: evidence found.
CVE published 10 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade Meridian to 2025.0.10 or 2024.3.13; Horizon to 36.0.4.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| The OpenNMS GroupMeridian | Affected
| Fixed in
|
| The OpenNMS GroupMeridian | Affected
| Fixed in
|
| The OpenNMS GroupHorizon | Affected
| Fixed in
|
GitHubMeridianpkg:github/MeridianOther threats | Affected
| Fixed in
|
GitHubHorizonpkg:github/HorizonOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix is available by upgrading to Meridian versions 2024.3.13 or 2025.0.10 and Horizon version 36.0.4 or later. Organizations should apply these updates promptly. Additionally, since these products are intended for use within private networks and not exposed directly to the Internet, ensure that deployment follows this guidance to reduce exposure. Patch status is confirmed by the vendor advisory.
Description
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.