In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_dualpi2: drain both C-queue and L-queue in dualpi2_change() Fix dualpi2_change() to correctly enforce updated limit and memlimit values after a configuration change of the dualpi2 qdisc. Before this patch, dualpi2_change() always attempted to dequeue packets via the root qdisc (C-queue) when reducing backlog or memory usage, and unconditionally assumed that a valid skb will be returned. When traffic classification results in packets being queued in the L-queue while the C-queue is empty, this leads to a NULL skb dereference during limit or memlimit enforcement. This is fixed by first dequeuing from the C-queue path if it is non-empty. Once the C-queue is empty, packets are dequeued directly from the L-queue. Return values from qdisc_dequeue_internal() are checked for both queues. When dequeuing from the L-queue, the parent qdisc qlen and backlog counters are updated explicitly to keep overall qdisc statistics consistent.

A flaw was found in the Linux kernel's `sch_dualpi2` qdisc (queueing discipline) component. When `dualpi2_change()` attempts to enforce updated limit and memory limit values, it may incorrectly try to dequeue packets from an empty C-queue while packets are present in the L-queue. This can lead to a NULL skb (socket buffer) dereference, potentially causing a system crash or a Denial of Service (DoS).

Red Hat Enterprise Linux 10 Not affected kernel Red Hat Enterprise Linux 6 Not affected 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 Not affected kernel Red Hat Enterprise Linux 9 Not affected kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-52997 https://nvd.nist.gov/vuln/detail/CVE-2026-52997 https://lore.kernel.org/linux-cve-announce/2026062446-CVE-2026-52997-545a@gregkh/T