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Concrete CmsApplication · Concretecms

CVE-2026-8414

HIGH · 8.8 CVSS v3.1 Published 2026-05-21
Fix available
A fix is available. Upgrade to 9.5.1 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
Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete/controllers/dialog/event/duplicate. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori (Tenzai) 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

Cross-Site Request Forgery (CSRF) vulnerability in Concrete CMS 9 before 9.5.0 at the event duplication endpoint (concrete/controllers/dialog/event/duplicate). The endpoint lacks proper anti-CSRF protection, allowing attackers to trick authenticated users into unknowingly executing duplicate event actions through malicious requests.

MitigationUpgrade to Concrete CMS 9.5.0 or later which includes CSRF token protection for the affected endpoint. If immediate patching is not possible, implement anti-CSRF tokens on the duplicate event form.

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:>= 9.0.0, < 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
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. Identify the installed Concrete CMS version
    Log into the Concrete CMS dashboard and navigate to Dashboard > System Information > Environment, or check the version file in your installation (typically found in concrete/config/app.php or the composer.json at the root). Compare the version number to the affected range: >= 9.0.0 and < 9.5.1.
    Affected if The installed version falls within >= 9.0.0 and < 9.5.1.
  2. Confirm the event duplicate controller exists
    On the web server hosting the Concrete CMS installation, navigate to the concrete/controllers/dialog/event/ directory and verify the duplicate.php controller file exists. This file handles the duplicate event functionality.
    Affected if The file concrete/controllers/dialog/event/duplicate.php exists on the server.
  3. Verify CSRF protection is missing on the duplicate endpoint
    Open the duplicate.php controller file and inspect its code for CSRF token validation. Look for calls to $this->validateCSRFToken() or similar anti-CSRF mechanisms within the duplicate action method. If no such validation exists, the endpoint is vulnerable.
    Affected if The duplicate.php controller does not contain CSRF token validation (no $this->validateCSRFToken() call or equivalent) in its duplicate action handler.
  4. Check if SameSite cookie attribute is properly configured
    Inspect the session cookie configuration in concrete/config/session.php or your web server configuration. Look for the SameSite attribute on the session cookie - it should be set to 'Lax' or 'Strict' for protection. If set to 'None' or missing entirely, CSRF protection is weakened.
    Affected if The session cookie SameSite attribute is set to 'None' or is not configured.

You are affected if your Concrete CMS version is 9.0.0 through 9.5.0 and the duplicate event controller lacks CSRF token validation.

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

Upgrade to Concrete CMS 9.5.0 or later which includes CSRF token protection for the affected endpoint. If immediate patching is not possible, implement anti-CSRF tokens on the duplicate event form.

Recommended fix High confidence

Concrete CMS 9.5.1 or latest 9.x stable release

  1. 1. Backup your Concrete CMS database and files before performing any upgrade
  2. 2. Download Concrete CMS version 9.5.1 or later from the official Concrete CMS website or repository
  3. 3. Replace the core Concrete CMS files with the new version, preserving your configuration and site-specific files
  4. 4. Run the database upgrade process through the Concrete CMS dashboard or CLI
  5. 5. Verify the CSRF protection is now applied to the /dialog/event/duplicate endpoint by testing the functionality
Caveat Review the Concrete CMS 9.5.x release notes for any breaking changes between your current version and 9.5.x 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
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2026-8414 in production — separate from our analysis above.

No notes yet

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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