What is CVE-2021-40102?

CVE-2021-40102 is a critical-severity vulnerability in Concretecms Concrete Cms, classified under Deserialization of Untrusted Data. CVSS score: 9.1/10. Published 2021-09-24.

How severe is CVE-2021-40102?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Deserialization in Concretecms Concrete Cms

CVE-2021-40102

An issue was discovered in Concrete CMS through 8.5.5. Arbitrary File deletion can occur via PHAR deserialization in is_dir (PHP Object Injection associated with the __wakeup magic method).

Vulnerability class: Insecure Deserialization

Published 2021-09-24 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H.

EPSS exploit prediction

EPSS: 0.013 (70.4th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 70th percentile — 70.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.013 · newest: 0.013 · change: 0.000

Affected products

Concretecms Concrete Cms

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

References

hackerone.com/reports/921288 (Permissions Required, Third Party Advisory)
documentation.concretecms.org/developers/introduction/version-history/856-relea… (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2021-40102?: CVE-2021-40102 is a critical-severity vulnerability in Concretecms Concrete Cms, classified under Deserialization of Untrusted Data. CVSS score: 9.1/10. Published 2021-09-24.
How severe is CVE-2021-40102?: Critical severity. CVSS v3 base score is 9.1 out of 10.