{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "2.0.1-rc.17"
              },
              {
                "fixed": "2.0.1-rc.18"
              },
              {
                "introduced": "0"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "DESCRIPTION"
            ]
          },
          "events": [
            {
              "introduced": "388b8f06e060a219d11bbc6be7f70f38d8bbea01"
            },
            {
              "fixed": "cb70e1ba513be827bb3698127bb7d06467412911"
            }
          ],
          "repo": "https://github.com/h3js/h3",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-fp4x-ggrf-wmc6"
  ],
  "database_specific": {
    "cna_assigner": "VulnCheck",
    "cwe_ids": [
      "CWE-601"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86205.json"
  },
  "details": "h3 versions before 2.0.1-rc.18 contain an open redirect vulnerability in the redirectBack() utility that fails to sanitize protocol-relative paths in the Referer header pathname. Attackers can craft a same-origin URL with a double-slash path segment that passes origin validation but produces a Location header interpreted by browsers as a protocol-relative redirect to an external domain.",
  "id": "CVE-2026-86205",
  "modified": "2026-09-10T03:30:21.961594181Z",
  "published": "2026-09-06T12:00:25.530Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86205.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/h3js/h3/security/advisories/GHSA-fp4x-ggrf-wmc6"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-86205"
    },
    {
      "type": "ADVISORY",
      "url": "https://www.vulncheck.com/advisories/h3-before-2.0.1-rc.18-open-redirect-via-redirectback"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "h3 before 2.0.1-rc.18 Open Redirect via redirectBack()"
}