CVE-2026-6733: Node.js Undici

Low severity, CVSS 3.7. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Node.js Undici: before 6.27.0 (fixed in 6.27.0); from 7.0.0, before 7.28.0 (fixed in 7.28.0); from 8.0.0, before 8.5.0 (fixed in 8.5.0)

Published 2026-06-17. Last modified 2026-06-27.