How severe is CVE-2021-25934?

CVE-2021-25934 has a CVSS score of 5.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-25934?

CVE-2021-25934 affects the following packages: org.opennms:opennms (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-25934?

The records we use list no patched version of org.opennms:opennms for CVE-2021-25934. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

How do I detect CVE-2021-25934 in my Maven dependencies?

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

How do I mitigate CVE-2021-25934 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2021-25934 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-25934, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-25934?

CVE-2021-25934 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 63th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-25934?

CVE-2021-25934 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2021-25934 published, and has it been updated?

CVE-2021-25934 was published on May 25, 2021 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

MEDIUM severity

CVE-2021-25934 — opennms

MEDIUMFix: OpenNMS/opennms@101e3aa

CVE-2021-25934 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in org.opennms:opennms. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

OpenNMS Horizon vulnerable to XSS

Also known asGHSA-9hhc-cc6c-99hh

Published

May 25, 2021

Updated

Oct 20, 2026

Affected

1 pkg

Patched

See advisory

Exploits

1 known

Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs63th percentile — riskier than 63% of all scored CVEsHighest risk

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:opennms

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

In OpenNMS Horizon, versions opennms-18.0.0-1 through opennms-27.1.0-1; OpenNMS Meridian, versions meridian-foundation-2015.1.0-1 through meridian-foundation-2019.1.18-1; meridian-foundation-2020.1.0-1 through meridian-foundation-2020.1.7-1 are vulnerable to Stored Cross-Site Scripting, since the function createRequisitionedNode() does not perform any validation checks on the input sent to the node-label parameter. Due to this flaw an attacker could inject an arbitrary script which will be stored in the database.

Affected Packages

1 total

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.opennms:opennms`	≥ 18.0.0-1	No fix

Affected Products

2 products · 3 configurations

Application

horizonopennms

≥ 18.0.0 && ≤ 27.1.0

range

Application

meridianopennms

≥ 2020.1.0 && ≤ 2020.1.7

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

In OpenNMS Horizon, versions opennms-18.0.0-1 through opennms-27.1.0-1; …

whitesourcesoftware.comNVDJun 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.opennms:opennms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
The records we use list no patched version of org.opennms:opennms for CVE-2021-25934. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
Mitigate without a patch
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

In OpenNMS Horizon, versions opennms-18.0.0-1 through opennms-27.1.0-1; OpenNMS Meridian, versions meridian-foundation-2015.1.0-1 through meridian-foundation-2019.1.18-1; meridian-foundation-2020.1.0-1 through meridian-foundation-2020.1.7-1 are vulnerable to Stored Cross-Site Scripting, since the function `createRequisitionedNode()` does not perform any validation checks on the input sent to the `node-label` parameter. Due to this flaw an attacker could inject an arbitrary script which will be stored in the database.

O3 Security · Impact-Aware SCA

Is CVE-2021-25934 in your dependencies?

Find it across Maven, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

5.4/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CWE Classification

CWE-79Cross-site Scripting (XSS)

Weaponization

No Nuclei template or Metasploit module yet. 1 public proof-of-concept reference is listed on this page.

OpenSSF Scorecard

Package health score

opennms

3.2/10

Code-Review5/10

Maintained10/10

Branch-ProtectionN/A

Assessed Oct 26, 2026

Timeline

Disclosed

May 25, 2021

First exploit

Jun 3, 2021

Last updated

Oct 20, 2026

Identifiers

CVE-2021-25934

GHSA-9hhc-cc6c-99hh

References

Advisorynvd.nist.gov · CVE 2021 25934 Fixgithub.com · 101e3aa06ec9a1f8f266335fc6f5685c062c6117 Fixgithub.com · eb08b5ed4c5548f3e941a1f0d0363ae4439fa98c Evidencewhitesourcesoftware.com · CVE 2021 25934

Related vulnerabilities

This CVE is medium severity; 8 of 8 other CVEs affecting opennms are rated as high or higher (top: high).

CVE-2023-0815CVE-2023-0867CVE-2023-0846CVE-2021-3396CVE-2021-25931CVE-2021-25933CVE-2021-25929CVE-2021-25930

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 20, 2026