Vulnerability-Lookup

CVE-2026-8426 (GCVE-0-2026-8426)

Vulnerability from cvelistv5 – Published: 2026-05-21 20:22 – Updated: 2026-05-22 12:13

Title

Concrete CMS 9.5.0 and below is vulnerable to CSRF on prepare_remote_upgrade() leading to one-request RCE via package overwrite

Summary

Concrete CMS 9.5.0 and below does not validate a CSRF token before processing requests to /dashboard/extend/update/prepare_remote_upgrade/<remoteMPID>. An attacker who controls the remote package returned for a known marketplace item ID can overwrite the package PHP on disk and force its upgrade() method to execute in a single browser navigation. This results in remote code execution as the web server user. In order to be vulnerable, the victim must be passing canInstallPackages, victim site must be connected to the Concrete marketplace; and the attacker controls the package returned for a marketplace item ID already installed on the victim site. 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.

Severity

7.5 (High)


                        
                          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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator (v2.0.3)

CWE

CWE-352 - Cross-Site request forgery (CSRF)
CWE-829 - Inclusion of functionality from untrusted control sphere

Assigner

ConcreteCMS

References

1 reference

URL	Tags
https://documentation.concretecms.org/9-x/develop…	release-notes

Impacted products

1 product

Vendor	Product	Version
Concrete CMS	Concrete CMS	Affected: 5.0 , ≤ 9.5.0 (git)

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-8426

Vulnerability from fkie_nvd - Published: 2026-05-21 21:16 - Updated: 2026-06-17 11:03

Severity

8.8 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Summary

References

	URL	Tags
	ff5b8ace-8b95-4078-9743-eac1ca5451de	https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes	Release Notes

Impacted products

	Vendor	Product	Version
	concretecms	concrete_cms	*

JSON

To clipboard

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    }
  ],
  "id": "CVE-2026-8426",
  "lastModified": "2026-06-17T11:03:55.633",
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          "scope": "UNCHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 5.9,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "HIGH",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "ACTIVE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "HIGH",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-8426",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-05-22T12:13:10.603126Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-05-21T21:16:34.243",
  "references": [
    {
      "source": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
      "tags": [
        "Release Notes"
      ],
      "url": "https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes"
    }
  ],
  "sourceIdentifier": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-352"
        },
        {
          "lang": "en",
          "value": "CWE-829"
        }
      ],
      "source": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
      "type": "Secondary"
    }
  ]
}

GHSA-5RJ5-GFMR-HRC3

Vulnerability from github – Published: 2026-05-21 21:30 – Updated: 2026-06-24 18:19

Summary

Concrete CMS does not validate a CSRF token before processing requests to `/dashboard/extend/update/prepare_remote_upgrade/<remoteMPID>`

Details

Concrete CMS 9.5.0 and below does not validate a CSRF token before processing requests to /dashboard/extend/update/prepare_remote_upgrade/. An attacker who controls the remote package returned for a known marketplace item ID can overwrite the package PHP on disk and force its upgrade() method to execute in a single browser navigation. This results in remote code execution as the web server user. In order to be vulnerable, the victim must be passing canInstallPackages, victim site must be connected to the Concrete marketplace; and the attacker controls the package returned for a marketplace item ID already installed on the victim site. The Concrete CMS security team thanks @maru1009 for reporting this issue.

Severity

7.5 (High)


                  
                    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

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "concrete5/concrete5"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "9.5.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-8426"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-352"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-24T18:19:48Z",
    "nvd_published_at": "2026-05-21T21:16:34Z",
    "severity": "HIGH"
  },
  "details": "Concrete CMS 9.5.0 and below does not validate a CSRF token before processing requests to /dashboard/extend/update/prepare_remote_upgrade/\u003cremoteMPID\u003e. An attacker who controls the remote package returned for a known marketplace item ID can overwrite the package PHP on disk and force its upgrade() method to execute in a single browser navigation. This results in remote code execution as the web server user.\u00a0\u00a0\u00a0In order to be vulnerable, the victim must be passing canInstallPackages,\u00a0victim site must be connected to the Concrete marketplace; and the attacker controls the package returned for a marketplace item ID already installed on the victim site.\u00a0The Concrete CMS security team thanks @maru1009\u00a0for reporting this issue.",
  "id": "GHSA-5rj5-gfmr-hrc3",
  "modified": "2026-06-24T18:19:48Z",
  "published": "2026-05-21T21:30:38Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-8426"
    },
    {
      "type": "WEB",
      "url": "https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/concretecms/concretecms"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Concrete CMS does not validate a CSRF token before processing requests to `/dashboard/extend/update/prepare_remote_upgrade/\u003cremoteMPID\u003e`"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-8426 (GCVE-0-2026-8426)

FKIE_CVE-2026-8426

GHSA-5RJ5-GFMR-HRC3

Tags

Sightings

Nomenclature