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CVE-2026-9816

Estado: AnalizadaAlta (8.3)—

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate BoardMember.Scheme* fields server-side on insert and archive-import paths which allows a board editor or non-guest team member to grant board admin to arbitrary users via POST /api/v2/boards/{boardID}/members and POST /api/v2/teams/{teamID}/archive/import.. Mattermost Advisory ID: MMSA-2026-00685

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Requiere acceso autenticado con privilegios (PR:L) en red remota; permite escalar permisos arbitrariamente. Fallo de validación de autorización (CWE-863) que otorga acceso a cuentas admin.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Privileged Account ManagementPassword PoliciesMulti-factor AuthenticationVulnerability ScanningUser Account ManagementThreat Intelligence Program

Tecnologías afectadas (1)

Mattermost — Mattermost Server

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2026-9816",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-9816",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-08-18T15:23:50.527601Z"
        }
      }
    ],
    "cvssMetricV31": [
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        "source": "responsibledisclosure@mattermost.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 8.3,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 5.5,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "responsibledisclosure@mattermost.com",
      "affectedData": [
        {
          "vendor": "Mattermost",
          "product": "Mattermost",
          "versions": [
            {
              "status": "affected",
              "version": "11.7.0",
              "versionType": "semver",
              "lessThanOrEqual": "11.7.6"
            },
            {
              "status": "affected",
              "version": "10.11.0",
              "versionType": "semver",
              "lessThanOrEqual": "10.11.21"
            },
            {
              "status": "affected",
              "version": "11.8.0",
              "versionType": "semver",
              "lessThanOrEqual": "11.8.3"
            },
            {
              "status": "unaffected",
              "version": "11.9.0"
            },
            {
              "status": "unaffected",
              "version": "11.7.7"
            },
            {
              "status": "unaffected",
              "version": "10.11.22"
            },
            {
              "status": "unaffected",
              "version": "11.8.4"
            }
          ],
          "defaultStatus": "unaffected"
        }
      ]
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  ],
  "published": "2026-08-17T22:17:27.217",
  "references": [
    {
      "url": "https://mattermost.com/security-updates",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "responsibledisclosure@mattermost.com"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "responsibledisclosure@mattermost.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-863"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate BoardMember.Scheme* fields server-side on insert and archive-import paths which allows a board editor or non-guest team member to grant board admin to arbitrary users via POST /api/v2/boards/{boardID}/members and POST /api/v2/teams/{teamID}/archive/import.. Mattermost Advisory ID: MMSA-2026-00685"
    }
  ],
  "lastModified": "2026-08-19T13:29:28.910",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "versionEndExcluding": "10.11.22",
              "versionStartIncluding": "10.11.0"
            },
            {
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "DA4EEA22-A3E7-43AF-91F7-4B597F944100",
              "versionEndExcluding": "11.7.7",
              "versionStartIncluding": "11.7.0"
            },
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              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "DE5EDDAA-76F1-4449-91BB-AFE517AD7B55",
              "versionEndExcluding": "11.8.4",
              "versionStartIncluding": "11.8.0"
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          ],
          "operator": "OR"
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  "sourceIdentifier": "responsibledisclosure@mattermost.com"
}