Security advisory

{
  "id": "eb053a1e01a3ee18bae315df0b0073bb50233f87488a820cd57e18db4321e597",
  "url": "https://osv.dev/vulnerability/CVE-2018-21257",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "CVE-2018-21257",
    "summary": "An issue was discovered in Mattermost Server before 5.1. It allows attackers to bypass intended access restrictions (for setting a channel header) via the Channel header slash command API.",
    "evidence": "osv:CVE-2018-21257",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2018-21257",
      "aliases": [
        "CVE-2018-21257"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/mattermost/mattermost",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "54994502241bf40bebd9a9d7719c58f708aef5b1"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "5.1.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v5.1.0-rc3",
            "v5.1.0-rc2",
            "v5.1.0-rc1",
            "v5.0.0-rc1",
            "v4.10.0-rc1",
            "v4.9.0-rc1",
            "v4.8.0-rc1",
            "v4.7.0-rc1",
            "v4.6.0-rc2",
            "v4.6.0-rc1",
            "v4.5.0-rc1",
            "v4.4.0-rc1",
            "v4.3.0-rc1",
            "v4.2.0-rc1",
            "v0.5.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2018-21257.json"
          }
        }
      ],
      "modified": "2026-10-24T10:30:22.670250304Z",
      "provider": "osv",
      "references": [
        "https://mattermost.com/security-updates/"
      ],
      "provider_metadata": {}
    },
    "related_cves": [
      {
        "value": "CVE-2018-21257",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 430738,
  "published_at": "2020-06-19T17:15:12.74+00:00"
}