CVE-2026-6733 | Impact: Undici's HTTP/1.1 client is vulnerable to response q… | CVSS 3.7 LOW

Description

Impact: Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets. An attacker-controlled upstream server can inject an unsolicited HTTP/1.1 response onto an idle socket after a request completes. When the client dispatches the next request on that socket, it associates the injected response with the new request, causing responses to be delivered to the wrong requests. This requires an attacker-controlled or compromised upstream HTTP/1.1 server and keep-alive connection reuse. Patches: Upgrade to undici v6.26.0, v7.28.0 or v8.5.0. Workarounds: Disable keep-alive connection reuse by setting keepAliveTimeout: 0 on the Client or Pool.

Metadata

CVE ID: CVE-2026-6733
State: PUBLISHED
Assigner: openjs
Reserved: 2026-04-20 22:44 UTC
Published: 2026-06-17 17:14 UTC
Last updated: 2026-06-17 18:30 UTC
Primary CWE: CWE-367
CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition
Vendor / Product: undici / undici
Sources: cve.org · NVD

Severity & Metrics

3.7 LOW CVSS 3.1

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

SSVC — CISA Coordinator

Exploitation: none
Automatable: no
Tech. Impact: partial

Affected products (1)

Vendor	Product	Platform	Versions
undici	undici	—	0 < 6.26.0, 6.26.0, 7.0.0 < 7.28.0, 7.28.0 …

Weakness (CWE)

CWE	Source	Description
CWE-367	cna	CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

CVSS scores (1)

Score	Severity	Version	Source	Vector
3.7	LOW	3.1	cna	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References (3)