Cross-team channel membership access

{
  "id": "6ef790d59a9c369aa38998f17eb4fa6023f386a9c6662b99f183bc32581ff010",
  "url": "https://osv.dev/vulnerability/CVE-2025-11777",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Cross-team channel membership access",
    "summary": "Mattermost versions 10.11.x <= 10.11.3, 10.5.x <= 10.5.11 fail to properly validate team membership permissions in the Add Channel Member API which allows users from one team to access user metadata and channel membership information from other teams via the API endpoint",
    "evidence": "osv:CVE-2025-11777",
    "products": [],
    "severity": "low",
    "structured": {
      "id": "CVE-2025-11777",
      "aliases": [
        "CVE-2025-11777",
        "GHSA-mqcj-8c2g-h97q",
        "GO-2025-4122"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/mattermost/mattermost",
              "type": "GIT",
              "events": [
                {
                  "introduced": "58bd34fd34cbd7d3da777d627b6cffdf8a532930"
                },
                {
                  "fixed": "9fa25cd55b43d735a39c6925d7e0021697ae049d"
                },
                {
                  "introduced": "5b955468ea1ea8b56c0fb10feb258a36a767d7bb"
                },
                {
                  "fixed": "83a5be3f9ed65d8457ab8cca853826d0c8425a8b"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "10.5.0"
                      },
                      {
                        "fixed": "10.5.12"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "10.11.0"
                      },
                      {
                        "fixed": "10.11.4"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v10.11.4-rc2",
            "v10.5.12-rc1",
            "v10.11.4-rc1",
            "v10.11.3",
            "v10.5.11",
            "v10.11.2-rc2",
            "v10.11.2",
            "v10.5.11-rc1",
            "v10.11.2-rc1",
            "v10.5.10",
            "v10.11.1",
            "v10.5.10-rc2",
            "v10.11.1-rc1",
            "v10.11.0-rc3",
            "v10.11.0",
            "mattermost-redux@10.11.0",
            "@mattermost/types@10.11.0",
            "@mattermost/client@10.11.0",
            "v10.5.10-rc1",
            "v10.5.9",
            "v10.5.9-rc4",
            "v10.5.9-rc3",
            "v10.5.9-rc2",
            "v10.5.9-rc1",
            "v10.5.8",
            "v10.5.8-rc1",
            "v10.5.7",
            "v10.5.6-rc1",
            "v10.5.6",
            "v10.5.5",
            "v10.5.5-rc1",
            "v10.5.4-rc2",
            "v10.5.4",
            "v10.5.4-rc1",
            "v10.5.3",
            "v10.5.3-rc1",
            "v10.5.2",
            "v10.5.1",
            "v10.5.1-rc2",
            "v10.5.1-rc1",
            "v10.5.0-rc6",
            "v10.5.0",
            "@mattermost/types@10.5.0",
            "@mattermost/client@10.5.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-11777.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:52.951945086Z",
      "provider": "osv",
      "references": [
        "https://mattermost.com/security-updates",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/11xxx/CVE-2025-11777.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-11777"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-863"
        ],
        "cna_assigner": "Mattermost",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "10.11.0"
                  },
                  {
                    "last_affected": "10.11.3"
                  },
                  {
                    "introduced": "10.5.0"
                  },
                  {
                    "last_affected": "10.5.11"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/11xxx/CVE-2025-11777.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-11777",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 521860,
  "published_at": "2025-11-13T17:32:03.975+00:00"
}