What is CVE-2021-40108?

CVE-2021-40108 is a high-severity vulnerability in Concretecms Concrete Cms, classified under Cross-Site Request Forgery (CSRF). CVSS score: 8.8/10. Published 2021-09-27.

How severe is CVE-2021-40108?

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

CSRF in Concretecms Concrete Cms

CVE-2021-40108

An issue was discovered in Concrete CMS through 8.5.5. The Calendar is vulnerable to CSRF. ccm_token is not verified on the ccm/calendar/dialogs/event/add/save endpoint.

Vulnerability class: CSRF (Cross-Site Request Forgery)

Published 2021-09-27 · last modified 2026-06-17.

CVSS v3 metric

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

EPSS exploit prediction

EPSS: 0.005 (40.7th percentile), scored 2026-10-07.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 41st percentile — 40.7% 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

Concretecms Concrete Cms

Weakness classification (CWE)

CWE-352 — Cross-Site Request Forgery (CSRF)

References

hackerone.com/reports/1102018 (Permissions Required)
documentation.concretecms.org/developers/introduction/version-history/856-relea… (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2021-40108?: CVE-2021-40108 is a high-severity vulnerability in Concretecms Concrete Cms, classified under Cross-Site Request Forgery (CSRF). CVSS score: 8.8/10. Published 2021-09-27.
How severe is CVE-2021-40108?: High severity. CVSS v3 base score is 8.8 out of 10.