Mattermost Desktop App plugin popout scheme validation bypass

{
  "id": "22f25759debaf4c717f2a698528e426533ad0b72365b78024c7ceeccbb396aa8",
  "url": "https://osv.dev/vulnerability/CVE-2026-75588",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Mattermost Desktop App plugin popout scheme validation bypass",
    "summary": "Mattermost Desktop App versions <=6.2 6.2.2.0 fail to validate the URL scheme when checking whether a target URL is internal to the connected server, which allows a network-positioned attacker to load a plugin popout window over an insecure connection via a link using a downgraded URL scheme. Mattermost Advisory ID: MMSA-2026-00717",
    "evidence": "osv:CVE-2026-75588",
    "products": [],
    "severity": "low",
    "structured": {
      "id": "CVE-2026-75588",
      "aliases": [
        "CVE-2026-75588"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/mattermost/desktop",
              "type": "GIT",
              "events": [
                {
                  "introduced": "200c274b361a2dcb7d7e8208adc44bdcd4645616"
                },
                {
                  "fixed": "99b6258eda51936ee4004a4e0175db06d65cc106"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:mattermost:mattermost_desktop:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "6.2.0"
                      },
                      {
                        "fixed": "6.2.3"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v6.2.3-rc.2",
            "v6.2.3-rc.1",
            "v6.2.2-mas.1",
            "v6.2.2",
            "v6.2.2-rc.1",
            "v6.2.1-mas.2",
            "v6.2.1",
            "v6.2.1-mas.1",
            "v6.2.1-rc.1",
            "v6.2.0-mas.1",
            "v6.2.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-75588.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:22.620139661Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/75xxx/CVE-2026-75588.json",
        "https://mattermost.com/security-updates",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-75588"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1287"
        ],
        "cna_assigner": "Mattermost",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "last_affected": "6.2.2"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/75xxx/CVE-2026-75588.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-75588",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 489201,
  "published_at": "2026-09-17T15:09:40.829+00:00"
}