Impact:
undici's cookie parser in parseSetCookie percent-decodes cookie values via qsUnescape, turning encoded sequences like %0D%0A, %00, %3B, and %3D into their literal byte equivalents. RFC 6265 §5.4 does not specify any decoding and browsers do not decode either.
Applications that parse a Set-Cookie header and then forward the parsed value into a response header (proxies, middleware, SSR frameworks) become vulnerable to HTTP response header injection: an attacker-controlled upstream can inject arbitrary Set-Cookie, Location, or Cache-Control headers into the application's downstream response, enabling session fixation, open redirect, or cache poisoning.
Affected applications are those that use undici's cookie parsing (parseSetCookie, parseCookie, getSetCookies) and forward the parsed cookie value into a response header.
This was introduced in undici 7.0.0 via PR #3789.
Patches:
Upgrade to undici v6.26.0, v7.28.0 or v8.5.0.
Workarounds:
If upgrade is not immediately possible, do not forward values returned by parseSetCookie/parseCookie/getSetCookies directly into response headers; sanitize the value first to strip or reject CR, LF, NUL, ;, and = bytes.
References
| Link | Resource |
|---|---|
| https://cna.openjsf.org/security-advisories.html | Vendor Advisory |
| https://github.com/nodejs/undici/security/advisories/GHSA-p88m-4jfj-68fv | Vendor Advisory Mitigation |
Configurations
Configuration 1 (hide)
|
History
25 Jun 2026, 17:43
| Type | Values Removed | Values Added |
|---|---|---|
| References | () https://cna.openjsf.org/security-advisories.html - Vendor Advisory | |
| References | () https://github.com/nodejs/undici/security/advisories/GHSA-p88m-4jfj-68fv - Vendor Advisory, Mitigation | |
| CPE | cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* | |
| First Time |
Nodejs
Nodejs undici |
17 Jun 2026, 20:20
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-06-17 18:18
Updated : 2026-06-25 17:43
NVD link : CVE-2026-9679
Mitre link : CVE-2026-9679
CVE.ORG link : CVE-2026-9679
JSON object : View
Products Affected
nodejs
- undici
CWE
CWE-93
Improper Neutralization of CRLF Sequences ('CRLF Injection')
