CRLF injection in undici - CVE-2026-9679
Published: June 17, 2026
Vulnerability identifier: #VU134756
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-9679
CWE-ID: CWE-93
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Node.js
Affected software:
undici
undici
Detailed vulnerability description
The vulnerability allows a remote attacker to inject arbitrary HTTP response headers.
The vulnerability exists due to improper neutralization of CRLF sequences in the parseSetCookie cookie parser when processing a crafted Set-Cookie header containing percent-encoded delimiter bytes. A remote attacker can supply a specially crafted upstream Set-Cookie header to inject arbitrary HTTP response headers.
Exploitation requires an application to parse a Set-Cookie header using parseSetCookie, parseCookie, or getSetCookies and then forward the parsed value into a downstream response header.
How to mitigate CVE-2026-9679
Install security update from vendor's website.