CVE-2026-8205: Concrete5/concrete5 Concrete CMS Is Vulnerable To Vulnerability

Q: What is CVE-2026-8205?

CVE-2026-8205 is a security vulnerability in Concrete5/concrete5 involving Concrete CMS is vulnerable to authorization bypass in the Calendar Block under CWE-425: Direct Request ('Forced Browsing').

Q: Which Concrete5/concrete5 versions are affected?

Affected versions include releases prior to 9.5.1 across affected packages: concrete5/concrete5.

Q: What version fixes CVE-2026-8205?

Upgrading to 9.5.1 (or the latest patched release for your respective branch) resolves the vulnerability.

Q: 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.

Q: What is the CVSS score of CVE-2026-8205?

CVE-2026-8205 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

Q: What CWE is associated with CVE-2026-8205?

CVE-2026-8205 is classified under CWE-425: Direct Request ('Forced Browsing') (The web application does not adequately enforce appropriate authorization on all restricted URLs, scripts, or files.).

Q: How can I check Packagist dependencies for CVE-2026-8205?

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.

MODERATE

Advisory Identifier: GHSA-46xh-7854-f568

CVSS 5.3

CWE-425

Published 2026-05-21

Advisory Summary

CVE-2026-8205 is a MODERATE (CVSS 5.3) concrete cms is vulnerable to vulnerability (CWE-425: Direct Request ('Forced Browsing')) affecting Concrete5/concrete5 libraries in the Packagist ecosystem. The issue involves concrete cms is vulnerable to authorization bypass in the calendar block. Remediation is available by upgrading affected packages to version 9.5.1.

CVE-2026-8205 at a Glance

CVE Identifier CVE-2026-8205

GHSA Identifier GHSA-46xh-7854-f568

Severity MODERATE

CVSS v3.1 Base Score 5.3

CWE Classification CWE-425: Direct Request ('Forced Browsing')

Affected Product Concrete5/concrete5

Package Ecosystem Packagist

Published Date 2026-05-21

Last Updated 2026-06-24

Security Impact

CVSS: 5.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N).

Attack Vector Network (AV:N)

Attack Complexity Low (AC:L)

Privileges Required None (PR:N)

User Interaction None (UI:N)

Scope Unchanged (S:U)

Confidentiality Low (C:L)

Integrity None (I:N)

Availability None (A:N)

How to Fix CVE-2026-8205

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-2026-8205, 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-425: Direct Request ('Forced Browsing'), where the web application does not adequately enforce appropriate authorization on all restricted urls, scripts, or files. 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 is vulnerable to authorization bypass in the Calendar Block since action_get_events does not check canView on the calendar which results in restricted event details being disclosed.

CVE-2026-8205 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-2026-8205 NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-8205

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-2026-8205?

CVE-2026-8205 is a security vulnerability in Concrete5/concrete5 involving Concrete CMS is vulnerable to authorization bypass in the Calendar Block under CWE-425: Direct Request ('Forced Browsing').

Which Concrete5/concrete5 versions are affected?

Affected versions include releases prior to 9.5.1 across affected packages: concrete5/concrete5.

What version fixes CVE-2026-8205?

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 is the CVSS score of CVE-2026-8205?

CVE-2026-8205 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

What CWE is associated with CVE-2026-8205?

CVE-2026-8205 is classified under CWE-425: Direct Request ('Forced Browsing') (The web application does not adequately enforce appropriate authorization on all restricted URLs, scripts, or files.).

How can I check Packagist dependencies for CVE-2026-8205?

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-46xh-7854-f568",
  "modified" : "2026-06-24T20:57:01Z",
  "published" : "2026-05-21T21:30:38Z",
  "aliases" : [ "CVE-2026-8205" ],
  "summary" : "Concrete CMS is vulnerable to authorization bypass in the Calendar Block",
  "details" : "Concrete CMS 9.5.0 and below is vulnerable to authorization bypass in the Calendar Block since action_get_events does not check canView on the calendar which results in restricted event details being disclosed.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/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-2026-8205"
  }, {
    "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-425" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-24T18:17:35Z",
    "nvd_published_at" : "2026-05-21T21:16:33Z"
  }
}

CVSS V3

5.3 MODERATE