Response queue poisoning on reused keep-alive sockets can lead to incorrect response delivery.

Summary

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. A flaw was found in undici. An attacker-controlled upstream server can exploit a vulnerability in Undici's HTTP/1.1 client, specifically related to response queue poisoning on reused keep-alive sockets. This allows the attacker to inject an unsolicited HTTP/1.1 response onto an idle socket. Consequently, when the client dispatches a new request on that socket, it may associate the injected response with the new request, leading to responses being delivered to unintended recipients or requests. This could result in a low impact on data integrity. Low: A flaw in Undici's HTTP/1.1 client, as used in various Red Hat products, allows an attacker-controlled upstream server to inject unsolicited responses onto reused keep-alive sockets. This can lead to incorrect response delivery, potentially impacting data integrity, but requires a compromised server and active keep-alive connections. Red Hat severity: Low — CVSS 3.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N). Weakness: CWE-940. Fixed by RHSA-2026:35841, RHSA-2026:35842 — update the affected packages (`sudo dnf update`). Affected Red Hat products: Red Hat Enterprise Linux 10.