CVE-2026-52997
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk7th percentile - higher than 7% of all known CVEs
Summary
In the Linux kernel's dualpi2 queuing discipline (net/sched), a vulnerability was found in the draining of both C-queue and L-queue during configuration change. The dualpi2_change() function incorrectly handled cases where packets were only in the L-queue, leading to a NULL pointer dereference.
Risk Assessment
An attacker can trigger a kernel panic by sending network traffic that lands in the L-queue and then performing a configuration change of the dualpi2 qdisc. This results in a denial of service (DoS).
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit 8e7b5a2c or later). If an update is not possible, temporarily disable the use of the dualpi2 qdisc.
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Original NVD description (English source)
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.