{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "versions": [
              {
                "introduced": "2.0.1-alpha.0"
              },
              {
                "fixed": "2.0.1-rc.17"
              }
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "388b8f06e060a219d11bbc6be7f70f38d8bbea01"
            }
          ],
          "repo": "https://github.com/h3js/h3",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-2j6q-whv2-gh6w"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-706"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33490.json"
  },
  "details": "H3 is a minimal H(TTP) framework. In versions 2.0.0-0 through 2.0.1-rc.16, the `mount()` method in h3 uses a simple `startsWith()` check to determine whether incoming requests fall under a mounted sub-application's path prefix. Because this check does not verify a path segment boundary (i.e., that the next character after the base is `/` or end-of-string), middleware registered on a mount like `/admin` will also execute for unrelated routes such as `/admin-public`, `/administrator`, or `/adminstuff`. This allows an attacker to trigger context-setting middleware on paths it was never intended to cover, potentially polluting request context with unintended privilege flags. Version 2.0.2-rc.17 contains a patch.",
  "id": "CVE-2026-33490",
  "modified": "2026-04-01T23:10:05.353841651Z",
  "published": "2026-03-26T17:19:15.956Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33490.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/h3js/h3/security/advisories/GHSA-2j6q-whv2-gh6w"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33490"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "h3: Missing Path Segment Boundary Check in `mount()` Causes Middleware Execution on Unrelated Prefix-Matching Routes"
}