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Concrete CMS CVE-2026-8238

| EUVD-2026-31354 MEDIUM
Missing Authorization (CWE-862)
2026-05-21 ConcreteCMS GHSA-qv3x-mffx-9gw8
6.3
CVSS 4.0
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CVSS VectorNVD

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
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

1
Analysis Generated
May 21, 2026 - 22:44 vuln.today

DescriptionNVD

Concrete CMS 9.5.0 and below is vulnerable to IDOR. The '/ccm/frontend/conversations/message_page' 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 Tristan Madani for reporting.

AnalysisAI

Insecure Direct Object Reference (IDOR) in Concrete CMS 9.5.0 and earlier exposes the full content of any conversation message through an unauthenticated frontend API endpoint, including messages from restricted pages, member-only areas, and the moderation queue. Unauthenticated remote attackers can enumerate message records and harvest file attachment download URLs by querying /ccm/frontend/conversations/message_page without credentials. …

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CVE-2026-8238 vulnerability details – vuln.today

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