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VulnerabilityPublished

CVE-2026-19135: The OpenNMS Group Meridian · Unsafe Reflection

Affects The OpenNMS Group MeridianSource CVE Database V5

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Not known to be exploited · CVSS 5.4 Medium : upgrade to 2025.0.9 or 2024.3.12 when convenient.

Data as of 11 Nov 2026, 23:24 UTC

CVSS 3.1 base score
5.4Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2025.0.9, 2024.3.12, 36.0.3
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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 11 Nov 2026.

What to do

Upgrade Meridian to 2025.0.9 or 2024.3.12; Horizon to 36.0.3.

Affected software

ProductAffectedFixed in
The OpenNMS GroupMeridianAffected
  • >=2025.0.0 <2025.0.9
Fixed in
  • 2025.0.9
The OpenNMS GroupMeridianAffected
  • >=2024.1.0 <2024.3.12
Fixed in
  • 2024.3.12
The OpenNMS GroupHorizonAffected
  • >=36.0.0 <36.0.3
Fixed in
  • 36.0.3
GitHubMeridianpkg:github/MeridianOther threatsAffected
  • >=2024.1.0 <2024.3.12
  • >=2025.0.0 <2025.0.9
Fixed in
  • 2024.3.12
  • 2025.0.9
GitHubHorizonpkg:github/HorizonOther threatsAffected
  • >=36.0.0 <36.0.3
Fixed in
  • 36.0.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade affected OpenNMS Meridian versions to 2024.3.12 or later, 2025.0.9 or later, and Horizon to 36.0.3 or later. Since these products are intended for private network deployment and not direct Internet exposure, ensure they remain protected behind appropriate network controls. Patch status is not explicitly stated as 'official-fix' in the vendor advisory, but the provided version upgrades are the recommended remediation. Check the vendor advisory for the latest guidance.

Description

A JEXL expression sandbox bypass exists in multiple versions of OpenNMS Meridian and Horizon. A low-privileged authenticated user can submit a crafted expression to the Measurements REST API that escapes the sandbox and loads arbitrary Java classes on the server. This can potentially allow an attacker to gain access to confidential information and compromise integrity. The solution is to upgrade to Meridian 2024.3.12, 2025.0.9 and Horizon 36.0.3 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.

References

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