CVE-2026-15157: undici vulnerable to CRLF Injection via blob-like body 'type' property
Affects undiciSource GCVE Database
Mentioned vulnerabilities
Not known to be exploited · CVSS 4.2 Medium : upgrade to 6.28.0 when convenient.
Data as of 1 Nov 2026, 22:58 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 17% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.28.0, 7.29.0, 8.9.0
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 3 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 1 Nov 2026.
What to do
Upgrade undici to 6.28.0; undici to 7.29.0; undici to 8.9.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| npmundici | Affected
| Fixed in
|
| npmundici | Affected
| Fixed in
|
| npmundici | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
### Impact When 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. The 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()`: ```javascript } else if (util.isBlobLike(body) && request.contentType == null && body.type) { headers.push('content-type', body.type) // bypasses isValidHeaderValue() } ``` The 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`. Same 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. ### Patches Patched in undici v6.28.0, v7.29.0, and v8.9.0. Users should upgrade to one of these versions or later. ### Workarounds - Set an explicit, validated `content-type` header on the request options (skips the vulnerable branch). - Use a native `Blob` (or `fetch-blob`) instead of a hand-rolled duck-typed object. - Reject control characters in the MIME type before assigning it to `.type`. - Use `fetch()` instead of the non-`fetch` APIs.
References
- github.com/nodejs/undici/security/advisories/GHSA-m8rv-5g2x-5cg5 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-15157 (opens in a new tab)
- github.com/nodejs/undici/commit/33928bc24f742ea8422ed90d17f2e0cc83e4d09d (opens in a new tab)
- github.com/nodejs/undici/commit/740a0b7c173cb4a83a5b693e96e8f3a116cfc400 (opens in a new tab)
- github.com/nodejs/undici/commit/7d3cf924c262c486bc77f951348f4e5c847b7b42 (opens in a new tab)
- cna.openjsf.org/security-advisories.html (opens in a new tab)
- github.com/nodejs/undici (opens in a new tab)
- github.com/nodejs/undici/releases/tag/v6.28.0 (opens in a new tab)
- github.com/nodejs/undici/releases/tag/v7.29.0 (opens in a new tab)
- github.com/nodejs/undici/releases/tag/v8.9.0 (opens in a new tab)