OpenNMS Horizon RCE via JEXL2 expression

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.8 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2021-3396: 2.37% estimated exploitation activity in the next 30 days; percentile 83.81 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

OpenNMS Meridian 2016, 2017, 2018 before 2018.1.25, 2019 before 2019.1.16, and 2020 before 2020.1.5, Horizon 1.2 through 27.0.4, and Newts <1.5.3 has Incorrect Access Control, which allows local and remote code execution using JEXL expressions.

Published by the source

24 May 2022, 17:42 UTC

Last modified by the source

3 Aug 2023, 18:43 UTC

Source last checked

26 Oct 2026, 16:11 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-c3mp-9vx3-2rvv

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# Patch Next advisory brief: CVE-2021-3396

Advisory: OpenNMS Horizon RCE via JEXL2 expression
IDs: CVE-2021-3396, GHSA-c3mp-9vx3-2rvv
Record: https://patchnext.com/advisories/cve-2021-3396 (revision 1, source checked 26 Oct 2026, 16:11 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.opennms.features:org.opennms.features.measurements 27.0.4; org.opennms:opennms-provision 27.0.4; org.opennms:opennms 27.0.4; org.opennms:opennms-util 27.0.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.opennms.features:org.opennms.features.measurements: affected >= 16.0.0, <= 27.0.3; fixed in 27.0.4
- Maven org.opennms:opennms-provision: affected >= 16.0.0, <= 27.0.3; fixed in 27.0.4
- Maven org.opennms:opennms: affected >= 16.0.0, <= 27.0.3; fixed in 27.0.4
- Maven org.opennms:opennms-util: affected >= 16.0.0, <= 27.0.3; fixed in 27.0.4

## Suggested inspection (read-only)
- Maven org.opennms.features:org.opennms.features.measurements: check the installed version with your package manager.
- Maven org.opennms:opennms-provision: check the installed version with your package manager.
- Maven org.opennms:opennms: check the installed version with your package manager.
- Maven org.opennms:opennms-util: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.opennms.features:org.opennms.features.measurements, org.opennms:opennms-provision, org.opennms:opennms, org.opennms:opennms-util.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-c3mp-9vx3-2rvv (GitHub-reviewed advisory GHSA-c3mp-9vx3-2rvv lists affected ranges: Maven org.opennms:opennms >=16.0.0 =16.0.0 =16.0.0 =16.0.0 <=27.0.3)

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