CVE-2021-39608Public exploitNetwork attack vector

Authenticated code execution via unrestricted plugin upload

Published Aug 23, 2021 · Updated Aug 4, 2024

Unrestricted file upload in FlatCore CMS 2.0.7 allows remote authenticated users to execute arbitrary PHP code through the add-on installer. The installer sends the supplied file to /acp/core/files.upload-script.php, which accepts a PHP plugin without restricting its dangerous file type and saves it under /upload/plugins. Administrator access and a valid CSRF token are required; the uploaded script then runs with the web server's privileges, enabling control of application data and service behavior.

CVSS severity7.2
High
EPSS probability45.95%
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 FlatCore CMS 2.0.7 allows remote authenticated users to execute arbitrary PHP code through the add-on installer. The installer sends the supplied file to /acp/core/files.upload-script.php, which accepts a PHP plugin without restricting its dangerous file type and saves it under /upload/plugins. Administrator access and a valid CSRF token are required; the uploaded script then runs with the web server's privileges, enabling control of application data and service behavior.

The record

CVE
CVE-2021-39608
Published
Aug 23, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-434, T1505.003
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Aug 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.0NIST NVDAV:N/AC:L/Au:S/C:C/I:C/A:C
7.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/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.

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 exploitPublished

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
T1505.003Server Software Component: Web Shell

Public exploit references

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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