CVE-2021-25933Network attack vector

Cross-user script execution via unchecked group fields

Published May 20, 2021 · Updated Apr 30, 2025

Stored XSS in OpenNMS Horizon through 27.1.0-1 and Meridian through 2020.1.6-1 allows remote authenticated users to inject script. The validateFormInput() function fails to reject HTML metacharacters in groupName and groupComment, causing saved group data to render as executable markup. High-privilege authenticated access is required to store the payload, and another administrator must view the group data; execution can initiate a malicious-file download.

CVSS severity4.8
Medium
EPSS probability1.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in OpenNMS Horizon through 27.1.0-1 and Meridian through 2020.1.6-1 allows remote authenticated users to inject script. The validateFormInput() function fails to reject HTML metacharacters in groupName and groupComment, causing saved group data to render as executable markup. High-privilege authenticated access is required to store the payload, and another administrator must view the group data; execution can initiate a malicious-file download.

The record

CVE
CVE-2021-25933
Published
May 20, 2021
Updated
Apr 30, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. May 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Apr 30, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

3.5National Vulnerability DatabaseAV:N/AC:M/Au:S/C:N/I:P/A:N
4.8National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
4.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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