Concrete CMS up to 9.5.0 Conversation Message message_page authorization

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Concrete CMS up to 9.5.0. The affected element is an unknown function of the file /ccm/frontend/conversations/message_page of the component Conversation Message Handler. This manipulation causes authorization. This vulnerability is tracked as CVE-2026-8238. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability has been found in Concrete CMS up to 9.5.0 and classified as problematic. Affected by this vulnerability is an unknown functionality of the file /ccm/frontend/conversations/message_page of the component Conversation Message Handler. The manipulation with an unknown input leads to a authorization vulnerability. The CWE definition for the vulnerability is CWE-862. The product does not perform an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect confidentiality. The summary by CVE is:

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.

The weakness was disclosed by Tristan Madani. It is possible to read the advisory at documentation.concretecms.org. This vulnerability is known as CVE-2026-8238 since 05/09/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 05/22/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Content Management System

Vendor

• Concrete

Name

• CMS

Version

• 9.0
• 9.1
• 9.2
• 9.3
• 9.4
• 9.5.0

License

• open-source

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CPE 2.2info

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