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
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.008 (54.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 54.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: +0.000
Affected products
- Altervista Flatnux — versions 2021-03.25
Weakness classification (CWE)
References
- www.exploit-db.com/exploits/51295 (exploit)
- flatnux.altervista.org/flatnux.html (product)
- www.vulncheck.com/advisories/flatnux-authenticated-file-upload-remote-code-exec… (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.