CVE-2026-6733CWE-367

undici vulnerable to HTTP response queue poisoning via keep-alive socket reuse

Low · published June 17, 2026

CVSS v3.1
3.7
EPSS
0%
Percentile
18.2
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
3.7 · LOW
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00270 · 18.2th percentile
Weakness
CWE-367 · Time-of-check Time-of-use (TOCTOU) Race Condition
Published
2026-06-17T17:14Z
EPSS history
Timeline
  • 17 JUN 17:14Z
    undici vulnerable to HTTP response queue poisoning via keep-alive socket reuse
    cvelistv5