{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "2.0.0-0"
              },
              {
                "fixed": "2.0.1-rc.15"
              },
              {
                "fixed": "2.0.1-rc.14"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "DESCRIPTION"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "91361835657410605f2041762da9e3f60d24ecfb"
            }
          ],
          "repo": "https://github.com/h3js/h3",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-3vj8-jmxq-cgj5"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-290"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33131.json"
  },
  "details": "H3 is a minimal H(TTP) framework. Versions 2.0.0-0 through 2.0.1-rc.14 contain a Host header spoofing vulnerability in the NodeRequestUrl (which extends FastURL) which allows middleware bypass. When event.url, event.url.hostname, or event.url._url is accessed, such as in a logging middleware, the _url getter constructs a URL from untrusted data, including the user-controlled Host header. Because H3's router resolves the route handler before middleware runs, an attacker can supply a crafted Host header (e.g., Host: localhost:3000/abchehe?) to make the middleware path check fail while the route handler still matches, effectively bypassing authentication or authorization middleware. This affects any application built on H3 (including Nitro/Nuxt) that accesses event.url properties in middleware guarding sensitive routes. The issue requires an immediate fix to prevent FastURL.href from being constructed with unsanitized, attacker-controlled input. Version 2.0.1-rc.15 contains a patch for this issue.",
  "id": "CVE-2026-33131",
  "modified": "2026-08-12T03:51:31.601446198Z",
  "published": "2026-03-20T10:16:29.556Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33131.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/h3js/h3/security/advisories/GHSA-3vj8-jmxq-cgj5"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33131"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "h3 has a middleware bypass with one gadget"
}