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Concrete CmsApplication · Concretecms

CVE-2026-8417

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 9.5.0 and below does not validate a CSRF token before processing requests to /dashboard/extend/update/do_update/<pkgHandle>. The do_update() method in concrete/controllers/single_page/dashboard/extend/update.php checks only canInstallPackages() before executing upgradeCoreData() and upgrade() on the named package's controller. Because the endpoint is a state-changing GET route with no token enforcement, an attacker can force an authenticated administrator to trigger a package upgrade via a single cross-site navigation.In order to be vulnerable, the victim must be passing canInstallPackages() and and a target package must already be already installed. 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/update/do_update/<pkgHandle> endpoint. The do_update() method only checks canInstallPackages() permission before executing upgradeCoreData() and upgrade() on installed packages, allowing attackers to force authenticated administrators to upgrade packages via malicious GET requests through cross-site navigation.

MitigationImplement CSRF token validation on the do_update() endpoint and convert the state-changing GET route to POST to prevent CSRF exploitation.

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
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 installed Concrete CMS version
    Locate the version file in your Concrete CMS installation (typically version.php or similar in the core directory), or check the dashboard at /dashboard/system/information. Compare the version number against the affected range: versions below 9.5.1 are potentially vulnerable.
    Affected if The installed version is 9.5.0 or lower (anything below 9.5.1).
  2. Locate the vulnerable update controller
    Navigate to the file concrete/controllers/single_page/dashboard/extend/update.php in your installation. Verify the file exists and examine the do_update() method.
    Affected if The file exists and contains a do_update() method without CSRF token validation.
  3. Verify missing CSRF token check in do_update method
    Inspect the do_update() method in update.php. Look for a call to validate the CSRF token (commonly via a token->validate() or similar function call). The vulnerability exists if the method only checks canInstallPackages() permission without calling a CSRF validation function before executing upgrade operations.
    Affected if The do_update() method does not contain a CSRF token validation call (such as $this->token->validate() or $this->getToken()->validate()) before performing package updates.

Your environment is affected if you are running Concrete CMS version 9.5.0 or below AND the do_update() method in concrete/controllers/single_page/dashboard/extend/update.php lacks CSRF token validation before executing upgrade operations.

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 CSRF token validation on the do_update() endpoint and convert the state-changing GET route to POST to prevent CSRF exploitation.

Recommended fix High confidence

Concrete CMS 9.5.1 or later

  1. Backup your Concrete CMS database and files before proceeding
  2. Download Concrete CMS version 9.5.1 or later from the official Concrete CMS website or repository
  3. Extract the new version files and replace the existing installation files
  4. Run the upgrade process by accessing your site (the upgrade typically runs automatically on first access after file replacement)
  5. Verify the installation was successful by logging into the dashboard
  6. Confirm the /dashboard/extend/update/do_update/<pkgHandle> endpoint now requires CSRF token validation
Caveat Standard minor version upgrade - review release notes for any configuration or theme changes

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
  • Testing3.0 h
  • Review / QA2.0 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-2026-8417 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