CVE-2026-52997

The CVE-2026-52997 issue affects the Linux kernel’s net/sched sch_dualpi2 qdisc. The root cause was that dualpi2_change() could attempt to dequeue from the C-queue even when it was empty while packets resided in the L-queue, leading to a NULL skb dereference during limit/memlimit enforcement. The...

kernel: sch_hfsc: Fix qlen accounting bug when using peek in hfsc_enqueue()

A flaw was found in the HFSC queueing discipline implementation in the Linux kernel. When a packet is enqueued and the child qdisc's peek function is called before properly updating the HFSC queue's length and backlog counters, a race condition can occur. In some cases, the peek operation may...

CVE-2025-21971 net_sched: Prevent creation of classes with TC_H_ROOT

In the Linux kernel, the following vulnerability has been resolved: netsched: Prevent creation of classes with TCHROOT The function qdisctreereducebacklog uses TCHROOT as a termination condition when traversing up the qdisc tree to update parent backlog counters. However, if a class is created wi...

CVE-2025-21971

Summary (CVE-2025-21971): In the Linux kernel, an issue in net_sched can cause incorrect parent backlog statistics when a Qdisc class is created with classid TC_H_ROOT (0xFFFFFFFF). The traversal in qdisc_tree_reduce_backlog() terminates at TC_H_ROOT instead of the actual root, which can lead to ...