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CVE-2026-9820

Status: AnalyzedLow (3.8)—

Mattermost versions 11.7.x <= 11.7.2, 10.11.x <= 10.11.19 fail to sanitize team objects returned by the scheme teams endpoint, which allows a user with the User Manager role to obtain invite links for private teams and use them to join or share access to those teams via the scheme teams API endpoint.. Mattermost Advisory ID: MMSA-2026-00671

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

Mattermost — Mattermost Server

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2026-9820",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-9820",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-07-13T13:09:24.482863Z"
        }
      }
    ],
    "cvssMetricV31": [
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        "source": "responsibledisclosure@mattermost.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 3.8,
          "attackVector": "NETWORK",
          "baseSeverity": "LOW",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "HIGH",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 2.5,
        "exploitabilityScore": 1.2
      }
    ]
  },
  "affected": [
    {
      "source": "responsibledisclosure@mattermost.com",
      "affectedData": [
        {
          "vendor": "Mattermost",
          "product": "Mattermost",
          "versions": [
            {
              "status": "affected",
              "version": "11.7.0",
              "versionType": "semver",
              "lessThanOrEqual": "11.7.2"
            },
            {
              "status": "affected",
              "version": "10.11.0",
              "versionType": "semver",
              "lessThanOrEqual": "10.11.19"
            },
            {
              "status": "unaffected",
              "version": "11.8.0"
            },
            {
              "status": "unaffected",
              "version": "11.7.3"
            },
            {
              "status": "unaffected",
              "version": "10.11.20"
            }
          ],
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-07-13T11:16:28.203",
  "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-862"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Mattermost versions 11.7.x <= 11.7.2, 10.11.x <= 10.11.19 fail to sanitize team objects returned by the scheme teams endpoint, which allows a user with the User Manager role to obtain invite links for private teams and use them to join or share access to those teams via the scheme teams API endpoint.. Mattermost Advisory ID: MMSA-2026-00671"
    }
  ],
  "lastModified": "2026-07-13T20:38:36.670",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "806B772A-4575-47F4-BD6B-7422C9045190",
              "versionEndExcluding": "10.11.20",
              "versionStartIncluding": "10.11.0"
            },
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              "versionEndExcluding": "11.7.3",
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          "operator": "OR"
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  "sourceIdentifier": "responsibledisclosure@mattermost.com"
}