What is CVE-2023-53956?

CVE-2023-53956 is a high-severity vulnerability in Altervista Flatnux, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 8.8/10. Published 2025-12-19.

How severe is CVE-2023-53956?

High severity. CVSS v3 base score is 8.8 out of 10.

Arbitrary file upload in Altervista Flatnux

CVE-2023-53956

Flatnux 2021-03.25 contains an authenticated file upload vulnerability that allows administrative users to upload arbitrary PHP files through the file manager. Attackers with admin credentials can upload malicious PHP scripts to the web root directory, enabling remote code execution on the server.

Vulnerability class: Unrestricted File Upload

EPSS: 0.007 (48.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Affected products

Altervista Flatnux — versions 2021-03.25

Weakness classification (CWE)

CWE-434 — Unrestricted Upload of File with Dangerous Type

References

disclosure@vulncheck.com (exploit)
disclosure@vulncheck.com (product)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2023-53956?: CVE-2023-53956 is a high-severity vulnerability in Altervista Flatnux, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 8.8/10. Published 2025-12-19.
How severe is CVE-2023-53956?: High severity. CVSS v3 base score is 8.8 out of 10.