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VulnerabilityPublished

CVE-2025-53121: The OpenNMS Group Horizon · XSS or 'Cross-site Scripting'

Affects The OpenNMS Group HorizonSource CVE Database V5

0

Not known to be exploited · CVSS 6.9 Medium : upgrade to 33.1.6 when convenient.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 4.0 base score
6.9Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 15% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 33.1.6
CVSS:4.0/AV:A/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 26 Jun 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: 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 26 Oct 2026.

What to do

Upgrade opennms/opennms to 33.1.6.

Affected software

ProductAffectedFixed in
GitHubopennms/opennmspkg:github/opennms/opennmsOther threatsAffected
  • <33.1.6
Fixed in
  • 33.1.6

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

AI-suggested

European organizations should immediately upgrade affected OpenNMS Horizon installations to version 33.1.6 or later, or Meridian to 2024.2.6 or later, as these versions contain patches for the stored XSS vulnerabilities. Beyond patching, organizations should ensure that Horizon and Meridian instances are strictly isolated within private networks and not exposed directly to the Internet or untrusted networks. Implement network segmentation and access controls to limit which users and systems can reach the management platform. Conduct regular security audits and input validation reviews on custom integrations or plugins that interact with Horizon to detect any additional injection points. Employ Content Security Policy (CSP) headers on the web interface to mitigate the impact of potential XSS exploitation. Monitor logs and user activity for unusual behavior that might indicate exploitation attempts. Train administrators on secure usage practices and the risks of stored XSS. Finally, review and harden authentication and authorization mechanisms to reduce the risk of privilege escalation if an XSS attack is successful.

Description

Multiple stored XSS were found on different nodes with unsanitized parameters in OpenMNS Horizon 33.0.8 and versions earlier than 33.1.6 on multiple platforms that allow an attacker to store on database and then inject HTML and/or Javascript on the page. The solution is to upgrade to Horizon 33.1.6, 33.1.7 or Meridian 2024.2.6, 2024.2.7 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. OpenNMS thanks Fábio Tomé for reporting this issue.

References

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