Which products and versions are affected by CVE-2026-8237?

Affected: Concrete CMS (Concretecms) versions >= 5.0; concrete5/concrete5 (composer). The full list is in the CVE brief.

Is CVE-2026-8237 being exploited in the wild?

It is not listed in any known-exploited vulnerabilities catalog.

Is CVE-2026-8237 in the CISA KEV catalog?

No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.

Is there a public exploit for CVE-2026-8237?

No public exploit code is known.

Is there a fix for CVE-2026-8237?

Fixed versions are available, including concrete5/concrete5 9.5.1, Concrete CMS 9.5.1.

How urgently should CVE-2026-8237 be patched?

Brandefense priority: routine patching, as no exploitation is known and its severity is moderate or low.

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Vulnerability Intelligence

CVE-2026-8237

Medium

Concrete CMS 9.5.0 and below is vulnerable to IDOR in the/ccm/frontend/conversations/message_detail endpoint

Published May 21, 2026 · Updated Sep 10, 2026 · Also known as GHSA-xpgc-7vc2-8725

Key Facts

Routine patching

CVE-2026-8237 is a medium-severity vulnerability (CVSS 6.3 v4) affecting Concrete CMS (Concretecms), concrete5/concrete5 (composer).
It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
EPSS estimates a 0.7% probability of exploitation in the next 30 days.
Fixed versions are available, including concrete5/concrete5 9.5.1, Concrete CMS 9.5.1.
Brandefense priority: routine patching, as no exploitation is known and its severity is moderate or low.

CVSS v4

6.3

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS (30-day exploit likelihood)

0.7%

Higher than 53.8% of all scored CVEs

Exploited in the wild

No known

Not in a known-exploited catalog

Public exploit code

None known

Get the full CVE-2026-8237 brief as a PDF

Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.

Description

Concrete CMS 9.5.0 and below is vulnerable to IDOR. The /ccm/frontend/conversations/message_detail endpoint returns the full content of any conversation message. An unauthenticated attacker can enumerate all conversation messages, including messages from restricted pages, member-only areas, and the moderation queue. File attachments with download URLs are also exposed. 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 Eldudareeno for reporting.

Affected Products

3 affected entries in total

Product	Affected versions	Fixed in
Concrete CMSConcretecms	>= 5.0	9.5.1
concrete5/concrete5composer	See advisory	9.5.1

Patched Releases

concrete5/concrete5

9.5.1

Concrete CMS

9.5.1

Timeline

Publicly disclosed
May 21, 2026
Last updated
Sep 10, 2026

Weakness Type

CWE-862 Missing Authorization

References

FAQ

Common Questions.

Concrete CMS 9.5.0 and below is vulnerable to IDOR.
Affected: Concrete CMS (Concretecms) versions >= 5.0; concrete5/concrete5 (composer). The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including concrete5/concrete5 9.5.1, Concrete CMS 9.5.1.
Brandefense priority: routine patching, as no exploitation is known and its severity is moderate or low.

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