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Concrete CmsApplication · Concretecms

CVE-2026-8413

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/page/bulk/design. 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

Concrete CMS 9 before 9.5.0 contains a CSRF vulnerability in the bulk page design functionality at concrete/controllers/dialog/page/bulk/design. An attacker can craft a malicious link that, when clicked by an authenticated user, triggers unwanted bulk design changes to pages. The high CVSS 8.8 score reflects network exploitability with low complexity and no authentication required, though the v4.0 vector suggests user interaction is needed.

MitigationUpgrade Concrete CMS to version 9.5.0 or later. Additionally, implement anti-CSRF tokens (CSRF tokens) on the affected form/action and enable SameSite cookie attributes as a defense-in-depth measure.

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 Concrete CMS version
    Locate the version file or dashboard (typically at /dashboard/system/information or check version.php in the application root)
    Affected if Installed version is 9.0.0 through 9.5.0 (inclusive)
  2. Locate the vulnerable controller file
    Check for the existence of concrete/controllers/dialog/page/bulk/design.php or equivalent in the installation directory
    Affected if The file exists and the CMS version falls within the affected range
  3. Verify bulk page design functionality is enabled
    Log in as an authenticated user and navigate to the pages bulk actions area or check if the bulk design feature is accessible in the dashboard
    Affected if Bulk page design functionality is available and the CMS version is before 9.5.1
  4. Check for CSRF token validation in the controller
    Inspect the bulk design controller code for anti-CSRF token validation (look for $this->validateCSRFToken() or similar token checks)
    Affected if No CSRF token validation is present in the bulk design controller

A user is affected if their Concrete CMS installation is version 9.0.0 through 9.5.0 and the bulk page design functionality is accessible without proper 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 Concrete CMS to version 9.5.0 or later. Additionally, implement anti-CSRF tokens (CSRF tokens) on the affected form/action and enable SameSite cookie attributes as a defense-in-depth measure.

Recommended fix High confidence

Concrete CMS 9.5.1 or later

  1. Backup your database and files before upgrading
  2. Download Concrete CMS version 9.5.1 or later from the official source (documentation.concretecms.org)
  3. Extract the new version files and upload them to your server, replacing the existing installation
  4. Run the concrete/bin/concrete or c5-concrete CLI tool to update the database schema if needed
  5. Verify the installation by logging into the admin dashboard
  6. Test that the bulk design functionality at concrete/controllers/dialog/page/bulk/design works correctly
Caveat Review the release notes for 9.5.x for any configuration or feature changes that may affect your site

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 / QA2.0 h
11.0 hours of engineering $1,930
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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-2026-8413 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