{"id":"CVE-2026-15157","aliases":["GHSA-m8rv-5g2x-5cg5"],"url":"https://o3.security/vulnerability/CVE-2026-15157","summary":"undici vulnerable to CRLF Injection via blob-like body 'type' property","details":"### Impact\n\nWhen an application passes a duck-typed blob-like body to undici's HTTP/1.1 dispatcher (via `request()`, `stream()`, `pipeline()`, or `dispatch()`) with a `.type` derived from untrusted input, an attacker can inject CRLF sequences (`\\r\\n`) to append arbitrary HTTP headers and potentially smuggle a second request past the upstream.\n\nThe vulnerable branch in `lib/dispatcher/client-h1.js` pushes `body.type` directly into the outgoing headers with no validation, while every other header path in undici goes through `isValidHeaderValue()`:\n\n```javascript\n} else if (util.isBlobLike(body) && request.contentType == null && body.type) {\n  headers.push('content-type', body.type)  // bypasses isValidHeaderValue()\n}\n```\n\nThe bug requires a hand-rolled duck-typed blob object or a Blob subclass with a controlled `.type`. Native `Blob` is safe because its constructor strips CRLF from `.type`. `fetch()` is unaffected because it validates via the `Headers` class. Ecosystem consumers that build duck-typed blob shapes from user input include `form-data-encoder`, `formdata-polyfill`, and `formdata-node`.\n\nSame defect class as `CVE-2022-35948` (explicit `content-type` sink, fixed in undici 5.8.2) and `CVE-2026-1527` (`upgrade` option sink, fixed in 6.24.0 / 7.24.0), both closed by adding `isValidHeaderValue()` on their respective sinks. This branch was missed.\n\n### Patches\n\nPatched in undici v6.28.0, v7.29.0, and v8.9.0. Users should upgrade to one of these versions or later.\n\n### Workarounds\n\n- Set an explicit, validated `content-type` header on the request options (skips the vulnerable branch).\n- Use a native `Blob` (or `fetch-blob`) instead of a hand-rolled duck-typed object.\n- Reject control characters in the MIME type before assigning it to `.type`.\n- Use `fetch()` instead of the non-`fetch` APIs.","published":"2026-07-29T21:17:44.740Z","modified":"2026-10-28T02:30:46.661697592Z","cvss":{"score":4.2,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N"},"epss":{"score":0.00193,"percentile":0.09182,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"undici","fixedVersion":"6.28.0"},{"ecosystem":"npm","name":"undici","fixedVersion":"7.29.0"},{"ecosystem":"npm","name":"undici","fixedVersion":"8.9.0"}],"fix":{"url":"https://github.com/nodejs/undici/commit/33928bc24f742ea8422ed90d17f2e0cc83e4d09d","label":"nodejs/undici@33928bc"},"references":[{"type":"ADVISORY","url":"https://cna.openjsf.org/security-advisories.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/15xxx/CVE-2026-15157.json"},{"type":"ADVISORY","url":"https://github.com/nodejs/undici/security/advisories/GHSA-m8rv-5g2x-5cg5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-15157"},{"type":"WEB","url":"https://github.com/nodejs/undici/commit/33928bc24f742ea8422ed90d17f2e0cc83e4d09d"},{"type":"WEB","url":"https://github.com/nodejs/undici/commit/740a0b7c173cb4a83a5b693e96e8f3a116cfc400"},{"type":"WEB","url":"https://github.com/nodejs/undici/commit/7d3cf924c262c486bc77f951348f4e5c847b7b42"},{"type":"PACKAGE","url":"https://github.com/nodejs/undici"},{"type":"WEB","url":"https://github.com/nodejs/undici/releases/tag/v6.28.0"},{"type":"WEB","url":"https://github.com/nodejs/undici/releases/tag/v7.29.0"},{"type":"WEB","url":"https://github.com/nodejs/undici/releases/tag/v8.9.0"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:46.661697592Z"}}