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Concrete CmsApplication · Concretecms

CVE-2021-40108

HIGH · 8.8 CVSS v3.1 Published 2021-09-27
Fix available
A fix is available. Upgrade to 8.5.6 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges

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
An issue was discovered in Concrete CMS through 8.5.5. The Calendar is vulnerable to CSRF. ccm_token is not verified on the ccm/calendar/dialogs/event/add/save endpoint.

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

The Calendar component in Concrete CMS through 8.5.5 lacks CSRF protection on the event creation endpoint. The server fails to validate the ccm_token security token when processing requests to ccm/calendar/dialogs/event/add/save, allowing attackers to trick authenticated users into creating unwanted calendar events via malicious HTML forms.

MitigationImplement proper ccm_token validation on the affected calendar event save endpoint to verify the CSRF token before processing any event creation requests.

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:< 8.5.6

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
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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 Concrete CMS version
    Locate the version file or dashboard: typically in /concrete/config.php or via Admin Dashboard > Dashboard > System Information > Version Information. Compare the installed version to the affected range (< 8.5.6).
    Affected if The installed version is 8.5.5 or earlier.
  2. Verify Calendar component is installed
    Navigate to the Concrete CMS dashboard and check if the Calendar feature is enabled. This can be done by visiting the page planner or checking for calendar-related permissions and functionality in the Admin Dashboard under 'Pages & Themes' or 'Add Functionality'.
    Affected if The Calendar component is installed and accessible to users.
  3. Confirm the vulnerable endpoint exists
    Inspect the web server for the path ccm/calendar/dialogs/event/add/save. This endpoint should be reachable via POST requests on the Concrete CMS installation. Check if the route is registered in the application's routing configuration.
    Affected if The endpoint ccm/calendar/dialogs/event/add/save is accessible on the server.
  4. Inspect CSRF token validation in the event save handler
    Examine the server-side code that handles the event save POST request. Look for ccm_token validation logic in the calendar event controller that processes requests to ccm/calendar/dialogs/event/add/save. Verify whether the code calls a token validation function (such as $this->validateCSRFToken() or similar) before processing event data.
    Affected if The event save handler lacks or bypasses ccm_token validation before processing the request.

A user is affected if their Concrete CMS installation is version 8.5.5 or earlier AND the Calendar component is in use AND the event save endpoint processes requests without validating the ccm_token security token.

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 8.5.6 or later
Fixed in 8.5.6
Interim mitigation

Implement proper ccm_token validation on the affected calendar event save endpoint to verify the CSRF token before processing any event creation requests.

Recommended fix High confidence

Concrete CMS 8.5.6

  1. 1. Create a full backup of the database and files for the Concrete CMS installation
  2. 2. Download Concrete CMS version 8.5.6 from the official concretecms.org website
  3. 3. Follow the official Concrete CMS upgrade documentation to apply the update
  4. 4. After upgrade, verify the calendar event creation functionality works correctly
  5. 5. Clear any application caches if applicable

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

Fix this in Concrete Cms Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.

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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-2021-40108 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