What is CVE-2021-40902?

CVE-2021-40902 is a medium-severity vulnerability in Flatcore Flatcore-Cms, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2022-06-13.

How severe is CVE-2021-40902?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Flatcore Flatcore-Cms

CVE-2021-40902

flatCore-CMS version 2.0.8 is affected by Cross Site Scripting (XSS) in the "Create New Page" option through the index page.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2022-06-13 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.005 (38.9th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 38.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Flatcore Flatcore-Cms — versions 2.0.8

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

github.com/flatCore/flatCore-CMS/issues/57 (Exploit, Third Party Advisory, Issue Tracking)

Frequently asked questions

What is CVE-2021-40902?: CVE-2021-40902 is a medium-severity vulnerability in Flatcore Flatcore-Cms, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2022-06-13.
How severe is CVE-2021-40902?: Medium severity. CVSS v3 base score is 5.4 out of 10.