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VulnerabilityPublished

CVE-2026-127235: The OpenNMS Group Meridian · Cross-site Scripting

Affects The OpenNMS Group MeridianSource CVE Database V5

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Not known to be exploited · CVSS 6.1 Medium · fixed in 2026.0.2 : update The OpenNMS Group Meridian when convenient.

Data as of 12 Nov 2026, 18:49 UTC

CVSS 3.1 base score
6.1Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (OpenNMS)CVSS 3.16.1
Patch
Available – fixed in 2026.0.2, 2025.0.12, 2024.3.15 +1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 12 Nov 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 12 Nov 2026.

What to do

Upgrade Meridian to 2026.0.2, 2025.0.12 or 2024.3.15; Horizon to 36.0.6.

Affected software

ProductAffectedFixed in
The OpenNMS GroupMeridianAffected
  • >=2026.0.0 <2026.0.2
Fixed in
  • 2026.0.2
The OpenNMS GroupMeridianAffected
  • >=2025.0.0 <2025.0.12
Fixed in
  • 2025.0.12
The OpenNMS GroupMeridianAffected
  • >=2024.1.0 <2024.3.15
Fixed in
  • 2024.3.15
The OpenNMS GroupHorizonAffected
  • >=36.0.0 <36.0.6
Fixed in
  • 36.0.6
GitHubMeridianpkg:github/MeridianOther threatsAffected
  • >=2024.1.0 <2024.3.15
  • >=2025.0.0 <2025.0.12
  • >=2026.0.0 <2026.0.2
Fixed in
  • 2024.3.15
  • 2025.0.12
  • 2026.0.2
GitHubHorizonpkg:github/HorizonOther threatsAffected
  • >=36.0.0 <36.0.6
Fixed in
  • 36.0.6

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

Description

A reflected cross-site scripting vulnerability exists in the web user interface of multiple versions of OpenNMS Meridian and Horizon. Several web UI pages copy request parameter values into the HTML response without correct contextual output encoding. A remote attacker can craft a link that runs arbitrary JavaScript in the OpenNMS origin when an authenticated user opens it. The script runs in the victim's browser with the victim's session, so the attacker can read page data and send same-origin requests as the victim. The fix encodes the affected request values. On pages that use AngularJS, the fix also stops client-side template evaluation of the reflected values. 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.

References

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