Vulnerability-Lookup

FKIE_CVE-2026-8204

Vulnerability from fkie_nvd - Published: 2026-05-21 21:16 - Updated: 2026-07-23 16:10

Severity

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Summary

Concrete CMS 9.5.0 and below is vulnerable to authorization Bypass in the Calendar Event Frontend Dialog which can allow cross-calendar data disclosure. A public calendar block can be used as a pivot point to access private calendar data. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 6.3 with vector 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. Thanks Winston Crooker for reporting.

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

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://github.com/concretecms/concretecms",
          "defaultStatus": "unaffected",
          "product": "Concrete CMS",
          "repo": "https://github.com/concretecms/concretecms",
          "vendor": "Concrete CMS",
          "versions": [
            {
              "lessThanOrEqual": "9.5.0",
              "status": "affected",
              "version": "5",
              "versionType": "git"
            }
          ]
        }
      ],
      "source": "ff5b8ace-8b95-4078-9743-eac1ca5451de"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "2E0D5AA2-E073-464B-9026-9A428B24ABFA",
              "versionEndExcluding": "9.5.1",
              "vulnerable": true
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          "operator": "OR"
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  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Concrete CMS 9.5.0 and below is vulnerable to authorization Bypass in the Calendar Event Frontend Dialog which can allow cross-calendar data disclosure. A public calendar block can be used as a pivot point to access private calendar data. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of\u00a06.3 with vector\u00a0CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks\u00a0Winston Crooker for reporting."
    },
    {
      "lang": "es",
      "value": "Concrete CMS 9.5.0 y versiones anteriores es vulnerable a una omisi\u00f3n de autorizaci\u00f3n en el Di\u00e1logo Frontend de Eventos del Calendario, lo que puede permitir la divulgaci\u00f3n de datos entre calendarios. Un bloque de calendario p\u00fablico puede ser utilizado como punto de pivote para acceder a datos de calendario privados. El equipo de seguridad de Concrete CMS otorg\u00f3 a esta vulnerabilidad una puntuaci\u00f3n CVSS v.4.0 de 6.3 con el vector 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. Gracias a Winston Crooker por informar."
    }
  ],
  "id": "CVE-2026-8204",
  "lastModified": "2026-07-23T16:10:00.137",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "cvssMetricV40": [
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        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.3,
          "baseSeverity": "MEDIUM",
          "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": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "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/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": "NONE",
          "vulnConfidentialityImpact": "LOW",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
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        "ssvcData": {
          "id": "CVE-2026-8204",
          "options": [
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            {
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            },
            {
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          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-05-22T12:27:29.187587Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-05-21T21:16:33.530",
  "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": [
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          "lang": "en",
          "value": "CWE-639"
        }
      ],
      "source": "ff5b8ace-8b95-4078-9743-eac1ca5451de",
      "type": "Secondary"
    }
  ]
}

CVE-2026-8204 (GCVE-0-2026-8204)

Vulnerability from cvelistv5 – Published: 2026-05-21 20:56 – Updated: 2026-05-22 12:27

Title

Concrete CMS 9.5.0 and below is vulnerable to Authorization Bypass in the Calendar Event Frontend Dialog

Summary

Severity

6.3 (Medium)


                        
                          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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-05-22 12:27 UTC

CWE

CWE-639 - Authorization bypass through User-Controlled key

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 , ≤ 9.5.0 (git)

Credits

Winston Crooker

Show details on NVD website

JSON

To clipboard

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      {
        "metrics": [
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            "other": {
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                "id": "CVE-2026-8204",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-22T12:27:29.187587Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-22T12:27:38.540Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
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        }
      ],
      "credits": [
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          "type": "finder",
          "value": "Winston Crooker"
        }
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          "url": "https://documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes"
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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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

FKIE_CVE-2026-8204

CVE-2026-8204 (GCVE-0-2026-8204)

Tags

Sightings

Nomenclature