{"id":"GHSA-5w89-w975-hf9q","revision":"e913fd386b024cb59df8374c0b29434f","records":[{"revision":"e913fd386b024cb59df8374c0b29434f","observedAt":"2026-10-24T13:17:17.793+00:00","statement":{"source":"osv","id":"GHSA-5w89-w975-hf9q","aliases":["CVE-2026-44373"],"title":"Nitro has a proxy scope bypass via percent-encoded path traversal in `routeRules`","description":"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's `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 — 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's base. The bytes forwarded upstream are unchanged when the request is allowed.\n\n> Note: the fix assumes the upstream does not double-decode percent-encoding. If your upstream decodes twice (`%252F → %2F → /`), 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.","state":0,"publishedAt":"2026-05-06T23:01:27+00:00","modifiedAt":"2026-05-14T20:48:31.940118+00:00","affected":[{"ecosystem":"npm","name":"nitro","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"3.0.260429-beta"}]}],"versions":[],"rawVersionEvidence":null},{"ecosystem":"npm","name":"nitropack","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"2.13.4"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/nitrojs/nitro/security/advisories/GHSA-5w89-w975-hf9q","https://nvd.nist.gov/vuln/detail/CVE-2026-44373","https://github.com/nitrojs/nitro/pull/4222","https://github.com/nitrojs/nitro/pull/4223","https://github.com/nitrojs/nitro","https://github.com/nitrojs/nitro/releases/tag/v2.13.4","https://github.com/nitrojs/nitro/releases/tag/v3.0.260429-beta"],"sourceUrl":"https://github.com/advisories/GHSA-5w89-w975-hf9q","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-5w89-w975-hf9q","identifiers":["GHSA-5w89-w975-hf9q","CVE-2026-44373"]},"retained":false,"historicalAffected":[]}],"coverage":[]}