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Concrete CmsApplication · Concretecms

CVE-2026-8239

MEDIUM · 5.3 CVSS v3.1 Published 2026-05-21
Fix available
A fix is available. Upgrade to 9.5.1 or later.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Concrete CMS 9.5.0 and below is vulnerable to IDOR. The '/ccm/frontend/conversations/get_rating' endpoint confirms existence and returns rating score for any message by ID. 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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

IDOR vulnerability in Concrete CMS where the '/ccm/frontend/conversations/get_rating' endpoint allows unauthenticated or unauthorized users to retrieve rating scores for any message by directly referencing its ID, confirming message existence and exposing data without ownership verification.

MitigationImplement proper authorization checks to verify the requesting user has permission to access the rating for the specified message ID before returning any data.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Concrete CmsApplication
Affected:< 9.5.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Concrete CMS version
    Navigate to the dashboard and go to Dashboard > System & Settings > Basics > Application > Version, or check the composer.json file in the web root for the 'concrete/core' version entry
    Affected if The installed version is less than 9.5.1 (e.g., 9.5.0, 9.4.x, 9.3.x, or any 8.x version)
  2. Verify conversations feature is enabled
    Log into the admin dashboard and navigate to Dashboard > System & Settings > Conversation Settings, or check the database table 'Config' for the key 'conversations.enabled' set to 1
    Affected if Conversations are enabled on the site (the feature must be active for the vulnerable endpoint to exist)
  3. Confirm the vulnerable endpoint exists
    Make a GET request to /ccm/frontend/conversations/get_rating without any authentication tokens or session cookies
    Affected if The endpoint responds (even with an error) instead of returning HTTP 401/403, indicating the route is registered and accessible to unauthenticated users
  4. Test IDOR vulnerability with message ID enumeration
    Send a GET request to /ccm/frontend/conversations/get_rating?messageID=1 (or any numeric ID) without authentication, then try different messageID values
    Affected if The endpoint returns rating data (or any JSON response with message details) for arbitrary message IDs without requiring authentication or authorization

The site is affected if it runs Concrete CMS version below 9.5.1, has the conversations feature enabled, and the /ccm/frontend/conversations/get_rating endpoint returns any rating data for unauthenticated requests with arbitrary message IDs.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 9.5.1 or later
Fixed in 9.5.1
Interim mitigation

Implement proper authorization checks to verify the requesting user has permission to access the rating for the specified message ID before returning any data.

Recommended fix High confidence

Concrete CMS 9.5.1

  1. Verify current Concrete CMS version by accessing the dashboard or checking the version file
  2. Backup the database and files before any upgrade
  3. Download Concrete CMS 9.5.1 from the official source (documentation.concretecms.org or concretecms.com)
  4. Follow the upgrade instructions in the Concrete CMS documentation for your specific deployment method
  5. After upgrading, verify the /ccm/frontend/conversations/get_rating endpoint now properly authorizes requests
  6. Test that conversation ratings can only be accessed by users with appropriate permissions
Caveat Review release notes for 9.5.1 for any configuration or feature changes before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Concrete Cms Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-8239 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data