CVE-2026-1527: ImpactWhen an application passes user-controlled input to the upgrade option of client.request(), an attacker can inject CRLF sequences (\r\n) to: * Inject…

medium4.6CVSS 3.1

AVNACLPRLUIRSUCLILAN

ImpactWhen an application passes user-controlled input to the upgrade option of client.request(), an attacker can inject CRLF sequences (\r\n) to:

* Inject arbitrary HTTP headers
* Terminate the HTTP request prematurely and smuggle raw data to non-HTTP services (Redis, Memcached, Elasticsearch)
The vulnerability exists because undici writes the upgrade value directly to the socket without validating for invalid header characters:

// lib/dispatcher/client-h1.js:1121
if (upgrade) {
header += `connection: upgrade\r\nupgrade: ${upgrade}\r\n`
}

Affected

6 ranges

Vendor	Product	Version range	Fixed in
debian	node-undici	< node-undici 7.24.5+dfsg+~cs3.2.0-1 (forky)	node-undici 7.24.5+dfsg+~cs3.2.0-1 (forky)
nodejs	undici	< 6.24.0	6.24.0
nodejs	undici	>= 7.0.0 < 7.24.0	7.24.0
undici	undici	< 6.24.0; 7.0.0 < 7.24.0	6.24.0; 7.0.0 < 7.24.0
undici	undici	>= 0 < 6.24.0	6.24.0
undici	undici	>= 7.0.0 < 7.24.0	7.24.0

CVSS provenance

nvdv3.14.6MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

osv4.6MEDIUM