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Concrete CmsApplication · Concretecms

CVE-2026-8140

MEDIUM · 6.5 CVSS v3.1 Published 2026-05-21
Fix available
A fix is available. Upgrade to after 9.5.0 or later.
See remediation →
72/100
Remediation priority · Elevated
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 9.5.0 and below does not validate a CSRF token before processing requests to /dashboard/extend/install/download/<remoteId>. The download() method in concrete/controllers/single_page/dashboard/extend/install.php checks only the canInstallPackages() permission before fetching a remote marketplace package and writing it to the server's DIR_PACKAGES directory. Because the endpoint is a state-changing GET route with no token enforcement, an attacker who can cause an authenticated administrator to visit a crafted page can force an arbitrary marketplace package to be downloaded. In order to be vulnerable, the victim must be passing canInstallPackages() and the site must be connected to the Concrete marketplace. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 7.5 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks  https://github.com/maru1009  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 9.5.0 and below lacks CSRF token validation on the /dashboard/extend/install/download/<remoteId> endpoint. The download() method only checks canInstallPackages() permission but accepts state-changing GET requests without token enforcement, allowing attackers to force authenticated administrators to download arbitrary marketplace packages to the server's DIR_PACKAGES directory.

MitigationImplement CSRF token validation on the download() method before processing requests, or convert the GET route to POST and enforce token verification. Consider disabling marketplace connections if not required.

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:<= 9.5.0

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
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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 /dashboard/system_information or check the version.php file in the application config directory
    Affected if Version is 9.5.0 or lower
  2. Verify marketplace connection status
    Check if the Concrete CMS site has a marketplace connection configured under /dashboard/system/environment/network
    Affected if Marketplace connection is enabled and configured
  3. Inspect package download directory
    Examine the contents of the DIR_PACKAGES directory (typically /packages or /application/packages) for unexpected or unauthorized packages
    Affected if Unknown or suspicious packages are present that were not intentionally installed
  4. Review admin user permissions
    Check which users have canInstallPackages() permission under /dashboard/system/permissions/access
    Affected if Untrusted or compromised admin accounts have package installation permissions
  5. Audit marketplace download logs
    Review server logs for requests to /dashboard/extend/install/download/ from unexpected IP addresses or during periods of inactivity
    Affected if Unrecognized or unauthorized download requests are logged

A user is affected if their Concrete CMS version is 9.5.0 or lower, the marketplace connection is enabled, and they have administrators who could be tricked into triggering unauthorized package downloads.

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 a release after 9.5.0
Interim mitigation

Implement CSRF token validation on the download() method before processing requests, or convert the GET route to POST and enforce token verification. Consider disabling marketplace connections if not required.

Recommended fix Moderate confidence

Concrete CMS 9.5.1 or later

  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 (concretecms.com).
  3. 3. Replace the existing installation files with the new version, preserving your configuration and custom files.
  4. 4. Run the upgrade process by accessing your site - the upgrade script should automatically run.
  5. 5. Verify that the /dashboard/extend/install/ endpoint now requires CSRF token validation.
  6. 6. Test that package installation from the marketplace still works correctly for users with canInstallPackages permission.
Caveat Minor: Review custom modifications to dashboard/extend/install.php as they may need adjustment for compatibility

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
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

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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-2026-8140 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