CVE-2026-19603

{
  "id": "CVE-2026-19603",
  "sourceIdentifier": "[email protected]",
  "published": "2026-10-16T07:17:12.750",
  "lastModified": "2026-10-29T18:08:56.407",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to sanitize the active channel field returned by the user status API endpoints, which allows an authenticated user to learn the channel ID of a private channel another user is actively viewing via the status endpoints, without being a member of that channel. Mattermost Advisory ID: MMSA-2026-00765"
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "Mattermost",
          "product": "Mattermost",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "11.9.0",
              "lessThanOrEqual": "11.9.1",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "11.8.0",
              "lessThanOrEqual": "11.8.5",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "11.7.0",
              "lessThanOrEqual": "11.7.10",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "11.10.0",
              "lessThanOrEqual": "11.10.1",
              "versionType": "semver",
              "status": "affected"
            },
            {
              "version": "11.11.0",
              "status": "unaffected"
            },
            {
              "version": "11.9.2",
              "status": "unaffected"
            },
            {
              "version": "11.8.6",
              "status": "unaffected"
            },
            {
              "version": "11.7.11",
              "status": "unaffected"
            },
            {
              "version": "11.10.2",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
          "baseScore": 4.3,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "LOW",
          "integrityImpact": "NONE",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 1.4
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-10-16T11:58:53.325388Z",
          "id": "CVE-2026-19603",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-201"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "11.7.0",
              "versionEndExcluding": "11.7.11",
              "matchCriteriaId": "C7DFF726-7FA7-48F9-90CE-3F6DAF6FA1C0"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "11.8.0",
              "versionEndExcluding": "11.8.6",
              "matchCriteriaId": "864932C7-FD92-48AC-8789-DF73D5CA9AAF"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "11.9.0",
              "versionEndExcluding": "11.9.2",
              "matchCriteriaId": "2F937268-2154-4B45-B9E0-8B3451070CD0"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "11.10.0",
              "versionEndExcluding": "11.10.2",
              "matchCriteriaId": "02B602D7-09A8-4AD1-A4A2-C70050E007AB"
            }
          ]
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://mattermost.com/security-updates",
      "source": "[email protected]",
      "tags": [
        "Vendor Advisory"
      ]
    }
  ]
}