CVE-2026-8140: Concrete5/concrete5 Concrete CMS Is Vulnerable To Vulnerability

HIGH
Advisory Identifier: GHSA-r42c-3rr2-jrfp
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CWE-352
Published
Advisory Summary

CVE-2026-8140 is a HIGH concrete cms is vulnerable to vulnerability (CWE-352: Cross-Site Request Forgery (CSRF)) affecting Concrete5/concrete5 libraries in the Packagist ecosystem. The issue involves concrete cms is vulnerable to cross-site request forgery. Remediation is available by upgrading affected packages to version 9.5.1.

CVE-2026-8140 at a Glance

CVE Identifier CVE-2026-8140
GHSA Identifier GHSA-r42c-3rr2-jrfp
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-352: Cross-Site Request Forgery (CSRF)
Affected Product Concrete5/concrete5
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-8140

To remediate this vulnerability, upgrade all affected Concrete5/concrete5 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

concrete5/concrete5 fixed: 9.5.1 
Upgrade concrete5/concrete5 to 9.5.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for concrete5/concrete5

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-8140, inspect your project dependencies for Concrete5/concrete5:

inspect dependencies for concrete5/concrete5

Analyze the terminal output to locate any version of Concrete5/concrete5 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 9.5.1), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-352: Cross-Site Request Forgery (CSRF), where the web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor. In Concrete5/concrete5, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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. Concrete CMS thanks https://github.com/maru1009  for reporting this issue.

CVE-2026-8140 Affected Concrete5/concrete5 Versions

1 component(s)
Fixed Versions:
9.5.1
Product / Package Ecosystem Affected Versions Fixed Version
concrete5/concrete5
 Packagist
< 9.5.1
9.5.1

References

NVD — CVE-2026-8140 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-8140
documentation.concretecms.org/9-x/developers/intr... WEB
https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes
Concrete5/concrete5 Source Repository REPOSITORY
https://github.com/concretecms/concretecms

Frequently Asked Questions

What is CVE-2026-8140?
CVE-2026-8140 is a security vulnerability in Concrete5/concrete5 involving Concrete CMS is Vulnerable to Cross-Site Request Forgery under CWE-352: Cross-Site Request Forgery (CSRF).
Which Concrete5/concrete5 versions are affected?
Affected versions include releases prior to 9.5.1 across affected packages: concrete5/concrete5.
What version fixes CVE-2026-8140?
Upgrading to 9.5.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is concrete5/concrete5 affected?
Yes, concrete5/concrete5 is affected in releases prior to 9.5.1. Upgrade your dependency to 9.5.1 or later.
What CWE is associated with CVE-2026-8140?
CVE-2026-8140 is classified under CWE-352: Cross-Site Request Forgery (CSRF) (The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.).
How can I check Packagist dependencies for CVE-2026-8140?
Run the dependency tree command: 'inspect dependencies for concrete5/concrete5'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-r42c-3rr2-jrfp",
  "modified" : "2026-06-23T22:58:55Z",
  "published" : "2026-05-21T21:30:37Z",
  "aliases" : [ "CVE-2026-8140" ],
  "summary" : "Concrete CMS is Vulnerable to Cross-Site Request Forgery",
  "details" : "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. Concrete CMS thanks https://github.com/maru1009  for reporting this issue.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "concrete5/concrete5"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "9.5.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-8140"
  }, {
    "type" : "WEB",
    "url" : "https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/concretecms/concretecms"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-352" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-23T22:58:55Z",
    "nvd_published_at" : "2026-05-21T21:16:33Z"
  }
}