« Volver al listado

CVE-2026-27656

Estado: AnalizadaMedia (6.1)—

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to properly validate user identity in the OpenID {{IsSameUser()}} comparison logic, which allows an attacker to take over arbitrary user accounts via an overly permissive substring matching flaw in the user discovery flow.. Mattermost Advisory ID: MMSA-2026-00590

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).

Tecnologías afectadas (1)

Mattermost — Mattermost Server

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2026-27656",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-27656",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-03-26T03:55:33.452102Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "responsibledisclosure@mattermost.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.7,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "REQUIRED",
          "attackComplexity": "HIGH",
          "availabilityImpact": "NONE",
          "privilegesRequired": "HIGH",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.2,
        "exploitabilityScore": 0.5
      },
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 6.1,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "HIGH",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.2,
        "exploitabilityScore": 0.9
      }
    ]
  },
  "affected": [
    {
      "source": "responsibledisclosure@mattermost.com",
      "affectedData": [
        {
          "vendor": "Mattermost",
          "product": "Mattermost",
          "versions": [
            {
              "status": "affected",
              "version": "11.4.0",
              "versionType": "semver",
              "lessThanOrEqual": "11.4.0"
            },
            {
              "status": "affected",
              "version": "11.3.0",
              "versionType": "semver",
              "lessThanOrEqual": "11.3.1"
            },
            {
              "status": "affected",
              "version": "11.2.0",
              "versionType": "semver",
              "lessThanOrEqual": "11.2.3"
            },
            {
              "status": "affected",
              "version": "10.11.0",
              "versionType": "semver",
              "lessThanOrEqual": "10.11.11"
            },
            {
              "status": "unaffected",
              "version": "11.5.0"
            },
            {
              "status": "unaffected",
              "version": "11.4.1"
            },
            {
              "status": "unaffected",
              "version": "11.3.2"
            },
            {
              "status": "unaffected",
              "version": "11.2.4"
            },
            {
              "status": "unaffected",
              "version": "10.11.12"
            }
          ],
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-03-25T17:16:56.797",
  "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-303"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to properly validate user identity in the OpenID {{IsSameUser()}} comparison logic, which allows an attacker to take over arbitrary user accounts via an overly permissive substring matching flaw in the user discovery flow.. Mattermost Advisory ID: MMSA-2026-00590"
    },
    {
      "lang": "es",
      "value": "Las versiones de Mattermost 11.4.x &lt;= 11.4.0, 11.3.x &lt;= 11.3.1, 11.2.x &lt;= 11.2.3, 10.11.x &lt;= 10.11.11 no validan correctamente la identidad del usuario en la lógica de comparación OpenID {{IsSameUser()}}, lo que permite a un atacante tomar el control de cuentas de usuario arbitrarias a través de un fallo de coincidencia de subcadenas excesivamente permisivo en el flujo de descubrimiento de usuarios. ID de aviso de Mattermost: MMSA-2026-00590"
    }
  ],
  "lastModified": "2026-06-17T10:27:28.430",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "D144BD1D-F65C-498D-BC8A-F3D718F47F4B",
              "versionEndExcluding": "10.11.12",
              "versionStartIncluding": "10.11.0"
            },
            {
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "2E3E9B61-F003-45E4-9A04-8015A5CB8558",
              "versionEndExcluding": "11.2.4",
              "versionStartIncluding": "11.2.0"
            },
            {
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "805ECFFC-82FD-4754-AF95-32167E1D41CB",
              "versionEndExcluding": "11.3.2",
              "versionStartIncluding": "11.3.0"
            },
            {
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "839BC7B7-28DF-4125-937A-8B0D2D6893C2",
              "versionEndExcluding": "11.4.1",
              "versionStartIncluding": "11.4.0"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "responsibledisclosure@mattermost.com"
}