Is CVE-2026-8239 in the CISA KEV catalog?

No. CVE-2026-8239 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-8239?

CVE-2026-8239 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2026-8239?

CVE-2026-8239 has an EPSS score of 0.19% (9th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-8239?

Upgrade concrete cms to 9.5.1 or later.

CVE & CISA-KEV Catalog

CVE-2026-8239

MEDIUM

5.3

CVSS v3

NVD

Description

Concrete CMS 9.5.0 and below is vulnerable to IDOR. The '/ccm/frontend/conversations/get_rating' endpoint confirms existence and returns rating score for any message by ID. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 6.3 with Vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Tristan Madani for reporting.

CWE-862Missing Authorization

How to fix

Remediation Available

concrete cmsNVD

Affected:< 9.5.1Fixed in:9.5.1CVE-2026-8239derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityNone

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Exploit Intelligence

0.19%probability of exploitation in 30 days

9thpercentile

Low risk: more likely to be exploited than 9% of all known CVEs.

References

Release Notes1

documentation.concretecms.org

Related Vulnerabilities

Other CWE-862 (Missing Authorization) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2021-39226	Critical	9.8	100%	KEV	Fix
CVE-2022-0543	Critical	10.0	100%	KEV	Fix
CVE-2021-21978	Critical	9.8	99%	-	Fix
CVE-2023-52163	High	8.8	96%	KEV	-
CVE-2022-1329	High	8.8	93%	-	-
CVE-2023-6875	Critical	9.8	90%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-26.