CVE-2026-10721: Concrete CMS PHP Object Injection Via unserialize() calls Vulnerability

HIGH
Advisory Identifier: GHSA-g82f-9pw7-773w
Share
CWE-502
Published
Advisory Summary

CVE-2026-10721 is a HIGH php object injection via unserialize() calls vulnerability (CWE-502: Deserialization of Untrusted Data) affecting Concrete CMS libraries in the Packagist ecosystem. The issue involves php object injection via unserialize() calls. Remediation is available by upgrading affected packages to version 9.5.2.

CVE-2026-10721 at a Glance

CVE Identifier CVE-2026-10721
GHSA Identifier GHSA-g82f-9pw7-773w
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-502: Deserialization of Untrusted Data
Affected Product Concrete CMS
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-10721

To remediate this vulnerability, upgrade all affected Concrete CMS 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: 9.5.2 
Upgrade concrete5/concrete5 to 9.5.2
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-2026-10721, inspect your project dependencies for Concrete CMS:

inspect dependencies for concrete5/concrete5

Analyze the terminal output to locate any version of Concrete CMS in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 9.5.2), 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 Concrete CMS, 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 9.5.2 is vulnerable to PHP Object Injection via unserialize() calls in the  in Permission, Cache, and Search components. An unauthenticated attacker may trigger arbitrary PHP object instantiation if a malicious serialized payload has been placed in the database. Concrete CMS thanks XananasX7 for reporting this issue.

CVE-2026-10721 Affected Concrete CMS Versions

1 component(s)
Fixed Versions:
9.5.2
Product / Package Ecosystem Affected Versions Fixed Version
concrete5/concrete5
 Packagist
< 9.5.2
9.5.2

References

NVD — CVE-2026-10721 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-10721
Concrete CMS Release RELEASE
https://documentation.concretecms.org/9-x/developers/introduction/version-history/952-release-notes
Concrete CMS Source Repository REPOSITORY
https://github.com/concretecms/concretecms

Frequently Asked Questions

What is CVE-2026-10721?
CVE-2026-10721 is a security vulnerability in Concrete CMS involving PHP Object Injection via unserialize() calls under CWE-502: Deserialization of Untrusted Data.
Which Concrete CMS versions are affected?
Affected versions include releases prior to 9.5.2 across affected packages: concrete5/concrete5.
What version fixes CVE-2026-10721?
Upgrading to 9.5.2 (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 9.5.2. Upgrade your dependency to 9.5.2 or later.
What CWE is associated with CVE-2026-10721?
CVE-2026-10721 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-2026-10721?
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-g82f-9pw7-773w",
  "modified" : "2026-08-12T23:21:28Z",
  "published" : "2026-06-10T09:31:57Z",
  "aliases" : [ "CVE-2026-10721" ],
  "summary" : "Concrete CMS: PHP Object Injection via unserialize() calls",
  "details" : "Concrete CMS below 9.5.2 is vulnerable to PHP Object Injection via unserialize() calls in the  in Permission, Cache, and Search components. An unauthenticated attacker may trigger arbitrary PHP object instantiation if a malicious serialized payload has been placed in the database. Concrete CMS thanks XananasX7 for reporting this issue.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/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" : "9.5.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-10721"
  }, {
    "type" : "WEB",
    "url" : "https://documentation.concretecms.org/9-x/developers/introduction/version-history/952-release-notes"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/concretecms/concretecms"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-12T23:21:28Z",
    "nvd_published_at" : "2026-06-10T08:16:22Z"
  }
}