CVE-2026-8237

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

6.3 MediumPublic exploitFix available

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: Low
Integrity: None
Availability: None

Exploit likelihood

0.64%Up 0.6 points since May 22, 2026

What each source reports

CVE List Score used 6.3

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

Record: CVE-2026-8237
CVSS 4.0: 6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Weakness: CWE-862
Updated: 2026-11-02

EUVDEUVD-2026-31352 6.3

Record: EUVD-2026-31352
CVSS 4.0: 6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-xpgc-7vc2-8725 6.3

Concrete CMS is vulnerable to IDOR

Record: GHSA-xpgc-7vc2-8725
CVSS 4.0: 6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Weakness: CWE-862
Updated: 2026-11-02

NVD 6.3

Record: CVE-2026-8237
CVSS 4.0: 6.3 MediumCVSS: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
CVSS 3.1: 5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness: CWE-862
Updated: 2026-11-02

OSV 6.3

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

Record: CVE-2026-8237
CVSS 4.0: 6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Weakness: CWE-862
Updated: 2026-11-02

OSVGHSA-xpgc-7vc2-8725 6.3

Concrete CMS is vulnerable to IDOR

Record: GHSA-xpgc-7vc2-8725
CVSS 4.0: 6.3 MediumCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Weakness: CWE-862
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`concrete5/concrete5` Packagist	before 9.5.1	9.5.1
`concrete5/concrete5` Packagist	before 9.5.1, plus listed versions 8.08.0.18.0.28.0.38.1.0 Show 45 moreShow less 8.2.08.2.0RC28.2.18.3.08.3.18.3.28.4.08.4.0RC38.4.0RC48.4.18.4.28.4.38.4.48.4.58.5.08.5.0RC18.5.0RC28.5.18.5.108.5.118.5.128.5.138.5.148.5.158.5.168.5.178.5.188.5.198.5.28.5.208.5.218.5.38.5.48.5.58.5.68.5.6RC18.5.78.5.88.5.99.0.09.0.0RC19.0.0RC39.0.0RC49.0.19.0.2	9.5.1

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
Source	Link	Date
Nuclei	Concrete CMS <= 9.5.0 - Unauthenticated Conversation Message Disclosure (IDOR)
PoC in GitHub	aj2108/CVE-2026-8237	2026-08-01

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, Nuclei, NVD, OSV, PoC in GitHub

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-8237 is a medium vulnerability (CVSS 6.3) in Concrete Cms Cms, published May 21, 2026. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 0.64%, the 51st percentile. Fixed in concrete5/concrete5 9.5.1.

References

This page doesn't list everything

Left out here: 39 versions. The JSON record has them.