CVE-2026-8237Network attack vector

Unauthenticated message disclosure via missing authorization

Published May 21, 2026 · Updated May 21, 2026

Missing authorization in Concrete CMS 9.5.0 and earlier allows remote attackers to read private conversation messages and attachment URLs. The /ccm/frontend/conversations/message_detail endpoint retrieves a client-selected message and returns its full content without checking the requester's access to that message. No account or user interaction is required, and enumerating message identifiers exposes restricted-page, member-only, and moderation-queue content.

CVSS severity6.3
Medium
EPSS probability0.64%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authorization in Concrete CMS 9.5.0 and earlier allows remote attackers to read private conversation messages and attachment URLs. The /ccm/frontend/conversations/message_detail endpoint retrieves a client-selected message and returns its full content without checking the requester's access to that message. No account or user interaction is required, and enumerating message identifiers exposes restricted-page, member-only, and moderation-queue content.

The record

CVE
CVE-2026-8237
Published
May 21, 2026
Updated
May 21, 2026
Vendor
Concrete CMS
Product
Concrete CMS
Classifications
CWE-862
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 21, 2026CVE publishedPublication date reported by the CVE source.
  2. May 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.0 <=9.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Concrete CMS · Concrete CMSversion=5.0 <=9.5.0

Published CVSS scores

6.3ConcreteCMSCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-862Missing Authorization

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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