CVE-2020-21474Network attack vector

Unauthenticated code execution via unrestricted file upload

Published Jun 20, 2023 · Updated Dec 10, 2024

Unrestricted file upload in NucleusCMS 3.71 allows remote attackers to execute arbitrary code through the skin-files endpoint. The /nucleus/plugins/skinfiles/ handler accepts a dangerous file type when the dir=rsd parameter is supplied, allowing server-side interpretation of uploaded code. No authentication or user interaction is required, and successful execution runs with the web service's privileges.

CVSS severity9.8
Critical
EPSS probability1.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unrestricted file upload in NucleusCMS 3.71 allows remote attackers to execute arbitrary code through the skin-files endpoint. The /nucleus/plugins/skinfiles/ handler accepts a dangerous file type when the dir=rsd parameter is supplied, allowing server-side interpretation of uploaded code. No authentication or user interaction is required, and successful execution runs with the web service's privileges.

The record

CVE
CVE-2020-21474
Published
Jun 20, 2023
Updated
Dec 10, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-434, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 20, 2023CVE publishedPublication date reported by the CVE source.
  2. Dec 10, 2024Record 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 privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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