What is CVE-2021-20725?

CVE-2021-20725 is a medium-severity vulnerability in Calendar01 Project, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-05-24.

How severe is CVE-2021-20725?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Calendar01 Project

CVE-2021-20725

Reflected cross-site scripting vulnerability in the admin page of [Calendar01] free edition ver1.0.1 and earlier allows a remote attacker to inject an arbitrary script via unspecified vectors.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-05-24 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.008 (54.3th percentile), scored 2026-10-04.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 54.3% 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

Calendar01 Project
PHP Factory [Calendar01] Free Edition — versions ver1.0.1 and earlier

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

www.php-factory.net/calendar/01.php (Product, Third Party Advisory)
jvn.jp/en/jp/JVN53910556/index.html (Third Party Advisory)

Frequently asked questions

What is CVE-2021-20725?: CVE-2021-20725 is a medium-severity vulnerability in Calendar01 Project, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-05-24.
How severe is CVE-2021-20725?: Medium severity. CVSS v3 base score is 6.1 out of 10.