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HIGH severity

OpenNMS Horizon RCE via Unsafe DeserializationGHSA-853f-x27w-8r74

HIGHFix: OpenNMS/opennms#2983

GHSA-853f-x27w-8r74 is a high-severity (CVSS 8.8) Deserialization of Untrusted Data vulnerability in org.opennms.core:org.opennms.core.daemon. A fix is available for org.opennms.core:org.opennms.core.daemon — see the affected versions and patch details below.

Also known asCVE-2020-12760
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
3.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs89th percentile — riskier than 89% of all scored CVEsHighest risk
0.92%1.96%3.00%4.04%1.5%3.5%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
☕org.opennms.core:org.opennms.core.daemon

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

An issue was discovered in OpenNMS Horizon before 26.0.1, and Meridian before 2018.1.19 and 2019 before 2019.1.7. The ActiveMQ channel configuration allowed for arbitrary deserialization of Java objects (aka ActiveMQ Minion payload deserialization), leading to remote code execution for any authenticated channel user regardless of its assigned permissions.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.opennms.core:org.opennms.core.daemonall versions26.0.1org.opennms.core:org.opennms.core.daemon:26.0.1

Affected Products

2 products · 3 configurations
Application
opennms horizonopennms
< 26.1.0
range
Application
opennms meridianopennms
≥ 2019 && < 2019.1.7
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.opennms.core:org.opennms.core.daemon, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.opennms.core:org.opennms.core.daemon to 26.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-853f-x27w-8r74 is resolved across your whole dependency graph.

  3. Workarounds

    Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Frequently Asked Questions

An issue was discovered in OpenNMS Horizon before 26.0.1, and Meridian before 2018.1.19 and 2019 before 2019.1.7. The ActiveMQ channel configuration allowed for arbitrary deserialization of Java objects (aka ActiveMQ Minion payload deserialization), leading to remote code execution for any authenticated channel user regardless of its assigned permissions.
O3 Security · Impact-Aware SCA

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OpenNMS Horizon RCE via Unsafe Deserialization