CVE-2026-3452: Concrete5/concrete5 Remote Code Execution Vulnerability

HIGH
Advisory Identifier: GHSA-gj26-w59c-29mf
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CWE-502
Published
Advisory Summary

CVE-2026-3452 is a HIGH remote code execution vulnerability (CWE-502: Deserialization of Untrusted Data) affecting Concrete5/concrete5 libraries in the Packagist ecosystem. The issue involves concrete cms vulnerable to remote code execution by stored php object injection. Remediation is available by upgrading affected packages to version 9.4.8.

CVE-2026-3452 at a Glance

CVE Identifier CVE-2026-3452
GHSA Identifier GHSA-gj26-w59c-29mf
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-502: Deserialization of Untrusted Data
Affected Product Concrete5/concrete5
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-3452

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: 9.4.8 
Upgrade concrete5/concrete5 to 9.4.8
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-2026-3452, 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 9.4.8), 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-502: Deserialization of Untrusted Data, where the product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid. 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 below version 9.4.8 is vulnerable to Remote Code Execution by stored PHP object injection into the Express Entry List block via the columns parameter. An authenticated administrator can store attacker-controlled serialized data in block configuration fields that are later passed to unserialize() without class restrictions or integrity checks.  The Concrete CMS security team thanks YJK ( @YJK0805 https://hackerone.com/yjk0805 ) of ZUSO ART https://zuso.ai/  for reporting.

CVE-2026-3452 Affected Concrete5/concrete5 Versions

1 component(s)
Fixed Versions:
9.4.8
Product / Package Ecosystem Affected Versions Fixed Version
concrete5/concrete5
 Packagist
< 9.4.8
9.4.8

References

NVD — CVE-2026-3452 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-3452
Concrete5/concrete5 Source Repository REPOSITORY
https://github.com/concretecms/concretecms/pull/12826/changes/167f16e4805d8ab546d2997c753ac21bf4854920
documentation.concretecms.org/9-x/developers/intr... WEB
https://documentation.concretecms.org/9-x/developers/introduction/version-history/948-release-notes
Concrete5/concrete5 Source Repository REPOSITORY
https://github.com/concretecms/concretecms

Frequently Asked Questions

What is CVE-2026-3452?
CVE-2026-3452 is a security vulnerability in Concrete5/concrete5 involving Concrete CMS vulnerable to Remote Code Execution by stored PHP object injection under CWE-502: Deserialization of Untrusted Data.
Which Concrete5/concrete5 versions are affected?
Affected versions include releases prior to 9.4.8 across affected packages: concrete5/concrete5.
What version fixes CVE-2026-3452?
Upgrading to 9.4.8 (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 9.4.8. Upgrade your dependency to 9.4.8 or later.
What CWE is associated with CVE-2026-3452?
CVE-2026-3452 is classified under CWE-502: Deserialization of Untrusted Data (The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.).
How can I check Packagist dependencies for CVE-2026-3452?
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-gj26-w59c-29mf",
  "modified" : "2026-03-04T21:32:21Z",
  "published" : "2026-03-04T03:31:34Z",
  "aliases" : [ "CVE-2026-3452" ],
  "summary" : "Concrete CMS vulnerable to Remote Code Execution by stored PHP object injection",
  "details" : "Concrete CMS below version 9.4.8 is vulnerable to Remote Code Execution by stored PHP object injection into the Express Entry List block via the columns parameter. An authenticated administrator can store attacker-controlled serialized data in block configuration fields that are later passed to unserialize() without class restrictions or integrity checks. \n\nThe Concrete CMS security team thanks YJK ( @YJK0805 https://hackerone.com/yjk0805 ) of  ZUSO ART https://zuso.ai/  for reporting.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "concrete5/concrete5"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "9.4.8"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-3452"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/concretecms/concretecms/pull/12826/changes/167f16e4805d8ab546d2997c753ac21bf4854920"
  }, {
    "type" : "WEB",
    "url" : "https://documentation.concretecms.org/9-x/developers/introduction/version-history/948-release-notes"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/concretecms/concretecms"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-04T21:32:21Z",
    "nvd_published_at" : "2026-03-04T02:15:54Z"
  }
}