{"id":"CVE-2025-21620","aliases":["GHSA-f27p-cmv8-xhm6"],"url":"https://o3.security/vulnerability/CVE-2025-21620","summary":"Deno's authorization headers not dropped when redirecting cross-origin","details":"### Summary\nWhen you send a request with the `Authorization` header to one domain, and the response asks to redirect to a different domain, Deno's`fetch()` redirect handling creates a follow-up redirect request that keeps the original `Authorization` header, leaking its content to that second domain.\n\n\n### Details\n\nThe [right behavior](https://fetch.spec.whatwg.org/#ref-for-cors-non-wildcard-request-header-name) would be to drop the `Authorization` header instead, in this scenario. The same is generally applied to `Cookie` and `Proxy-Authorization` headers, and is done for not only host changes, but also protocol/port changes. Generally referred to as \"origin\".\n\nThe [documentation](https://docs.deno.com/runtime/reference/web_platform_apis/#:~:text=Deno%20does%20not%20follow%20the,leaking%20authenticated%20data%20cross%20origin.) states: \n> Deno does not follow the same-origin policy, because the Deno user agent currently does not have the concept of origins, and it does not have a cookie jar. This means Deno **does not need** to protect against leaking authenticated data cross origin \n\n### Reproduction\n```ts\nconst ac = new AbortController()\n\nconst server1 = Deno.serve({ port: 3001, signal: ac.signal }, (req) => {\n  return new Response(null, {\n    status: 302,\n    headers: {\n      'location': 'http://localhost:3002/redirected'\n    },\n  })\n})\n\nconst server2 = Deno.serve({ port: 3002, signal: ac.signal }, (req) => {\n  const body = JSON.stringify({\n    url: req.url,\n    hasAuth: req.headers.has('authorization'),\n  })\n  return new Response(body, {\n    status: 200,\n    headers: {'content-type': 'application/json'},\n  })\n})\n\nasync function main() {\n  const response = await fetch(\"http://localhost:3001/\", {\n    headers: {authorization: 'Bearer foo'}\n  })\n  const body = await response.json()\n  \n  ac.abort()\n  \n  if (body.hasAuth) {\n    console.error('ERROR: Authorization header should not be present after cross-origin redirect')\n  } else {\n    console.log('SUCCESS: Authorization header is not present after cross-origin redirect')\n  }\n}\n\nsetTimeout(main, 500)\n```\n","published":"2025-01-06T22:26:40.723Z","modified":"2026-08-12T03:51:13.376148778Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"crates.io","name":"deno_fetch","fixedVersion":"0.204.0"},{"ecosystem":"crates.io","name":"deno","fixedVersion":null},{"ecosystem":"crates.io","name":"deno","fixedVersion":"2.1.2"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21620.json"},{"type":"ADVISORY","url":"https://github.com/denoland/deno/security/advisories/GHSA-f27p-cmv8-xhm6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21620"},{"type":"PACKAGE","url":"https://github.com/denoland/deno"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:13.376148778Z"}}