What is CVE-2021-40098?

CVE-2021-40098 is a critical-severity vulnerability in Concretecms Concrete Cms, classified under Path Traversal. CVSS score: 9.8/10. Published 2021-09-27.

How severe is CVE-2021-40098?

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

Path Traversal in Concretecms Concrete Cms

CVE-2021-40098

An issue was discovered in Concrete CMS through 8.5.5. Path Traversal leading to RCE via external form by adding a regular expression.

Vulnerability class: Path Traversal (Directory Traversal)

Published 2021-09-27 · 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: 0.016 (75.2th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 75th percentile — 75.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.016 · newest: 0.016 · change: 0.000

Affected products

Concretecms Concrete Cms

Weakness classification (CWE)

CWE-22 — Path Traversal

References

hackerone.com/reports/1102080 (Permissions Required, Third Party Advisory)
documentation.concretecms.org/developers/introduction/version-history/856-relea… (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2021-40098?: CVE-2021-40098 is a critical-severity vulnerability in Concretecms Concrete Cms, classified under Path Traversal. CVSS score: 9.8/10. Published 2021-09-27.
How severe is CVE-2021-40098?: Critical severity. CVSS v3 base score is 9.8 out of 10.