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CVE-2026-28735

Estado: AnalizadaMedia (5.4)—

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628

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)

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{
  "id": "CVE-2026-28735",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
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        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-28735",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-05-22T16:55:25.541191Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "responsibledisclosure@mattermost.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.4,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 2.5,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "responsibledisclosure@mattermost.com",
      "affectedData": [
        {
          "vendor": "Mattermost",
          "product": "Mattermost",
          "versions": [
            {
              "status": "affected",
              "version": "11.6.0",
              "versionType": "semver",
              "lessThanOrEqual": "11.6.0"
            },
            {
              "status": "affected",
              "version": "11.5.0",
              "versionType": "semver",
              "lessThanOrEqual": "11.5.3"
            },
            {
              "status": "affected",
              "version": "11.4.0",
              "versionType": "semver",
              "lessThanOrEqual": "11.4.4"
            },
            {
              "status": "affected",
              "version": "10.11.0",
              "versionType": "semver",
              "lessThanOrEqual": "10.11.14"
            },
            {
              "status": "unaffected",
              "version": "11.7.0"
            },
            {
              "status": "unaffected",
              "version": "11.6.1"
            },
            {
              "status": "unaffected",
              "version": "11.5.4"
            },
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              "status": "unaffected",
              "version": "11.4.5"
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            {
              "status": "unaffected",
              "version": "10.11.15"
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          "defaultStatus": "unaffected"
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  ],
  "published": "2026-05-22T17:16:46.260",
  "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 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628"
    },
    {
      "lang": "es",
      "value": "Versiones de Mattermost 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 no validan el alcance del token OAuth en la devolución de llamada, lo que permite a un usuario autenticado de Mattermost obtener acceso a repositorios privados mediante la modificación del parámetro de alcance en la URL de autorización de GitHub. ID de aviso de Mattermost: MMSA-2026-00628"
    }
  ],
  "lastModified": "2026-07-23T16:10:00.137",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "vulnerable": true,
              "matchCriteriaId": "6696A83A-CD06-45BD-A4C1-16A09C4CA15B",
              "versionEndExcluding": "10.11.15",
              "versionStartIncluding": "10.11.0"
            },
            {
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
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              "matchCriteriaId": "617D4791-A087-42E8-BF73-B39B30CB29C8",
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}