Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-08-22T00:00:00 kernel: tcp: fix TFO max_qlen accounting across reuseport migration 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CWE-191

In the Linux kernel, the following vulnerability has been resolved: tcp: fix TFO max_qlen accounting across reuseport migration A listener's TCP_FASTOPEN max_qlen stops being accurate and lets through far more pending Fast Open requests than it was configured for. This only shows up with SO_REUSEPORT listener migration, where closing a listener hands its still-pending TFO children over to a surviving one. fastopenq.qlen is charged in tcp_fastopen_create_child() when the child is created and uncharged in reqsk_fastopen_remove() when the handshake completes. The uncharge follows rsk_listener of the request the child points at, and inet_reqsk_clone() has repointed the child at a new request owned by the new listener, so the ++ and the -- land on two different sockets. The new listener's qlen drifts negative and its limit no longer binds. Charge the new listener during migration, like reqsk_queue_migrated() already does for queue->young and queue->qlen.

A flaw was found in the Linux kernel's TCP Fast Open (TFO) implementation. During SO_REUSEPORT listener migration, the system incorrectly accounts for pending TCP Fast Open requests. This can lead to a Denial of Service (DoS) by allowing an excessive number of Fast Open requests, potentially exhausting system resources.

Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Out of support scope kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Not affected kernel Red Hat Enterprise Linux 8 Not affected kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-74696 https://nvd.nist.gov/vuln/detail/CVE-2026-74696 https://lore.kernel.org/linux-cve-announce/2026082234-CVE-2026-74696-3187@gregkh/T