CVE-2023-53956Public exploitNetwork attack vector

Authenticated code execution via unrestricted PHP upload

Published Dec 19, 2025 · Updated Dec 19, 2025

Unrestricted file upload in Flatnux 2021-03.25 allows remote authenticated users to execute PHP code through the file manager. The filemanager.php upload handler accepts a multipart PHP file and writes it beneath a web-accessible media path without blocking executable types. Administrative credentials and a valid CSRF token are required; uploaded scripts execute with the web server process privileges.

CVSS severity8.7
High
EPSS probability0.77%
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 Flatnux 2021-03.25 allows remote authenticated users to execute PHP code through the file manager. The filemanager.php upload handler accepts a multipart PHP file and writes it beneath a web-accessible media path without blocking executable types. Administrative credentials and a valid CSRF token are required; uploaded scripts execute with the web server process privileges.

The record

CVE
CVE-2023-53956
Published
Dec 19, 2025
Updated
Dec 19, 2025
Vendor
Flatnux
Product
Flatnux
Classifications
CWE-434, T1505.003
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Dec 19, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 19, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2021-03.25

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Flatnux · Flatnuxversion=2021-03.25

Published CVSS scores

8.8VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
8.7VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA: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 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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