{"id":"CVE-2026-1527","aliases":["GHSA-4992-7rv2-5pvq"],"url":"https://o3.security/vulnerability/CVE-2026-1527","summary":"undici is vulnerable to CRLF Injection via upgrade option","details":"### Impact\n\nWhen an application passes user-controlled input to the `upgrade` option of `client.request()`, an attacker can inject CRLF sequences (`\\r\\n`) to:\n\n1. Inject arbitrary HTTP headers\n2. Terminate the HTTP request prematurely and smuggle raw data to non-HTTP services (Redis, Memcached, Elasticsearch)\n\nThe vulnerability exists because undici writes the `upgrade` value directly to the socket without validating for invalid header characters:\n\n```javascript\n// lib/dispatcher/client-h1.js:1121\nif (upgrade) {\n  header += `connection: upgrade\\r\\nupgrade: ${upgrade}\\r\\n`\n}\n```\n\n### Patches\n\n Patched in the undici version v7.24.0 and v6.24.0. Users should upgrade to this version or later.\n\n### Workarounds\n\nSanitize the `upgrade` option string before passing to undici:\n\n```javascript\nfunction sanitizeUpgrade(value) {\n  if (/[\\r\\n]/.test(value)) {\n    throw new Error('Invalid upgrade value')\n  }\n  return value\n}\n\nclient.request({\n  upgrade: sanitizeUpgrade(userInput)\n})\n```","published":"2026-03-12T20:17:18.984Z","modified":"2026-10-28T02:31:05.420599761Z","cvss":{"score":4.6,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N"},"epss":{"score":0.00276,"percentile":0.19504,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"undici","fixedVersion":"6.24.0"},{"ecosystem":"npm","name":"undici","fixedVersion":"7.24.0"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/nodejs/undici/"},{"type":"WEB","url":"https://hackerone.com/reports/3487198"},{"type":"ADVISORY","url":"https://cna.openjsf.org/security-advisories.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/1xxx/CVE-2026-1527.json"},{"type":"ADVISORY","url":"https://github.com/nodejs/undici/security/advisories/GHSA-4992-7rv2-5pvq"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-1527"},{"type":"PACKAGE","url":"https://github.com/nodejs/undici"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:31:05.420599761Z"}}