Mattermost Server exposes sensitive user credentials during shared channel membership synchronization

{
  "id": "fa0cd112b0cb997f13ce102d1d1c8b1d4df5ba06b30dd6c1071bcfaeff35b99c",
  "url": "https://osv.dev/vulnerability/CVE-2025-9076",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Mattermost Server exposes sensitive user credentials during shared channel membership synchronization",
    "summary": "Mattermost versions 10.10.x <= 10.10.1 fail to properly sanitize user data during shared channel membership synchronization, which allows malicious or compromised remote clusters to access sensitive user information via unsanitized user objects. This vulnerability affects Mattermost Server instances with shared channels enabled.",
    "evidence": "osv:CVE-2025-9076",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2025-9076",
      "aliases": [
        "CVE-2025-9076",
        "GHSA-3vcm-c42p-3hhf",
        "GO-2025-3950"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/mattermost/mattermost",
              "type": "GIT",
              "events": [
                {
                  "introduced": "c8bd5c937551a4e9ad23f5a4fd8aaf7604d046dd"
                },
                {
                  "fixed": "70c3cb2c1eef66484d5455217295684a49b7c3f1"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "10.10.0"
                      },
                      {
                        "fixed": "10.10.2"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v10.10.2-rc4",
            "v10.10.2-rc3",
            "v10.10.2-rc2",
            "v10.10.2-rc1",
            "v10.10.1",
            "v10.10.1-rc1",
            "v10.10.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-9076.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:45.329579841Z",
      "provider": "osv",
      "references": [
        "https://mattermost.com/security-updates",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/9xxx/CVE-2025-9076.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-9076"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-862"
        ],
        "cna_assigner": "Mattermost",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "10.10.0"
                  },
                  {
                    "last_affected": "10.10.1"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/9xxx/CVE-2025-9076.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-9076",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 513435,
  "published_at": "2025-09-15T10:06:15.094+00:00"
}