What is CVE-2020-21359?

CVE-2020-21359 is a critical-severity vulnerability in Maccms, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 9.8/10. Published 2021-08-11.

How severe is CVE-2020-21359?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Arbitrary file upload in Maccms

CVE-2020-21359

An arbitrary file upload vulnerability in the Template Upload function of Maccms10 allows attackers bypass the suffix whitelist verification to execute arbitrary code via adding a character to the end of the uploaded file's name.

Vulnerability class: Unrestricted File Upload

Published 2021-08-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.017 (76.7th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 77th percentile — 76.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.017 · newest: 0.017 · change: 0.000

Affected products

Maccms — versions 10.0

Weakness classification (CWE)

CWE-434 — Unrestricted Upload of File with Dangerous Type

References

github.com/magicblack/maccms10/issues/80 (Exploit, Third Party Advisory, Issue Tracking)

Frequently asked questions

What is CVE-2020-21359?: CVE-2020-21359 is a critical-severity vulnerability in Maccms, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 9.8/10. Published 2021-08-11.
How severe is CVE-2020-21359?: Critical severity. CVSS v3 base score is 9.8 out of 10.