{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "nitro"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.0.260429-beta"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "nitropack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.13.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44373"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-06T23:01:27Z",
    "nvd_published_at": "2026-05-13T21:16:48Z",
    "severity": "MODERATE"
  },
  "details": "A proxy route rule like:\n\n```ts\nrouteRules: {\n  \"/api/orders/**\": { proxy: { to: \"http://upstream/orders/**\" } }\n}\n```\n\nis intended to limit the proxy to URLs under `/api/orders/`. Before the patch, an attacker could bypass that scope by sending percent-encoded path traversal (`..%2f`) in the URL, causing Nitro to forward a request that the upstream resolved outside the configured scope. Example exploit:\n\n```\nGET /api/orders/..%2fadmin%2fconfig.json\n```\n\nNitro sees `..%2f` as opaque characters at match time, the `/api/orders/**` rule matched, and the raw path was forwarded to the upstream as `/orders/..%2fadmin/config.json`. An upstream that decodes `%2F` to  `/` then resolved `..` and can serve `/admin/config.json` outside the intended scope.\n\n### Are you affected?\n\nUsers may be affected if **ALL** of the following are true:\n\n1. Their project uses Nitro\u0027s `routeRules` with a `proxy` entry (`{ proxy: { to: \"...\" } }`).\n2. The proxy `to` value uses a `/**` wildcard suffix to forward sub-paths.\n3. The **upstream** behind the proxy decodes `%2F` as `/` before routing or filesystem lookup.\n4. Proxy route rules are _not_ handled natively at CDN (nitro v3 and vercel)\n\nWhether the bypass actually leaks data depends on the upstream. Modern JS frameworks keep `%2F` opaque per RFC 3986 and are safe by construction. \n\n- **Safe examples:** H3 v2, Express v5, Hono v4 \u2014 modern JS frameworks keep `%2F` opaque per RFC 3986.\n- **Vulnerable examples:** naive imlementations that decodes the URL, static file servers, CGI dispatchers, Python `os.path`-based routing, anything sitting behind another layer that decodes `%2F` (common in microservice meshes).\n\n## Impact\n\nAny HTTP path reachable from the Nitro server to the upstream could be requested, regardless of the configured `/**` scope. In typical deployments (API gateway, BFF, microservice proxy) this could expose internal admin endpoints, secrets endpoints, or other services the developer believed the scope rule fenced off.\n\n## Patched versions\n\nUpgrade to one of:\n\n- [2.13.4](https://github.com/nitrojs/nitro/releases/tag/v2.13.4) or later (https://github.com/nitrojs/nitro/pull/4223) \n- [3.0.260429-beta](https://github.com/nitrojs/nitro/releases/tag/v3.0.260429-beta) or later (https://github.com/nitrojs/nitro/pull/4222)\n\nThe fix canonicalizes the incoming pathname before building the upstream URL and rejects requests with `400 Bad Request` if the resolved path would escape the rule\u0027s base. The bytes forwarded upstream are unchanged when the request is allowed.\n\n\u003e Note: the fix assumes the upstream does not double-decode percent-encoding. If your upstream decodes twice (`%252F \u2192 %2F \u2192 /`), it remains your responsibility to harden it. **Single-decode is standard**.\n\n## Credits\n\nReported by [@mHe4am](https://github.com/mHe4am) ([@he4am on HackerOne](https://hackerone.com/he4am)) via the [Vercel Open Source](https://hackerone.com/vercel-open-source?type=team) program.",
  "id": "GHSA-5w89-w975-hf9q",
  "modified": "2026-05-14T20:42:49Z",
  "published": "2026-05-06T23:01:27Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nitrojs/nitro/security/advisories/GHSA-5w89-w975-hf9q"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44373"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nitrojs/nitro/pull/4222"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nitrojs/nitro/pull/4223"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nitrojs/nitro"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nitrojs/nitro/releases/tag/v2.13.4"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nitrojs/nitro/releases/tag/v3.0.260429-beta"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Nitro has a proxy scope bypass via percent-encoded path traversal in `routeRules`"
}