GHSA-XPVF-6QCC-9JQC

Vulnerability from github – Published: 2026-03-16 15:30 – Updated: 2026-03-18 16:09
VLAI
Summary
Mattermost fails to validate team-specific upload_file permissions
Details

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553

Severity
4.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost/server/v8"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "8.0.0-20260107144005-c7f6efdfb035"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.3.2-0.20260107144005-c7f6efdfb035"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "10.11.0-rc1"
            },
            {
              "fixed": "10.11.11"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.2.0-rc1"
            },
            {
              "fixed": "11.2.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/mattermost/mattermost-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.3.0-rc1"
            },
            {
              "fixed": "11.3.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-4265"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-18T16:09:03Z",
    "nvd_published_at": "2026-03-16T14:20:19Z",
    "severity": "MODERATE"
  },
  "details": "Mattermost versions 11.3.x \u003c= 11.3.0, 11.2.x \u003c= 11.2.2, 10.11.x \u003c= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553",
  "id": "GHSA-xpvf-6qcc-9jqc",
  "modified": "2026-03-18T16:09:03Z",
  "published": "2026-03-16T15:30:46Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-4265"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mattermost/mattermost/commit/c7f6efdfb035490f494b3177996ee5f4b278c988"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mattermost/mattermost"
    },
    {
      "type": "WEB",
      "url": "https://mattermost.com/security-updates"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mattermost fails to validate team-specific upload_file permissions"
}



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