EUVD-2026-38865
GHSA-qc77-246g-gj7g
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Local access with CAP_NET_ADMIN (PR:L) required to reconfigure qdisc; no confidentiality or integrity impact, only availability via kernel panic.
Primary rating from NVD.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionNVD
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.
AnalysisAI
NULL pointer dereference in the Linux kernel's sch_dualpi2 queuing discipline (net/sched) allows a local attacker with low privileges to crash the kernel, causing a denial of service. The flaw exists in dualpi2_change(), which enforces updated queue limits after a qdisc reconfiguration: when traffic is exclusively queued in the L-queue and the C-queue is empty, the function unconditionally dereferences the NULL skb returned by the C-queue dequeue path, triggering a kernel panic. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires three concurrent conditions: (1) the target kernel must have sch_dualpi2 compiled in or loaded as a module (CONFIG_NET_SCH_DUALPI2), as the dualpi2 qdisc is not active by default; (2) the attacker must have CAP_NET_ADMIN capability within the relevant network namespace - achievable for the root user, for containers run with elevated privileges, or for unprivileged users in their own network namespaces on kernels with user namespace support enabled; (3) the attacker must enqueue traffic into the L-queue (low-latency queue) of an active dualpi2 qdisc such that the C-queue is empty, then invoke a qdisc parameter change (tc qdisc change) to trigger dualpi2_change(). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The overall real-world risk is moderate-to-low. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local user with CAP_NET_ADMIN capability - such as a container with elevated network privileges in a multi-tenant environment - configures a dualpi2 qdisc on a network interface and generates L4S-marked traffic that fills the L-queue while keeping the C-queue empty. The attacker then modifies the qdisc's limit or memlimit parameter via tc, triggering dualpi2_change(). … |
| Remediation | The primary fix is to upgrade to a patched stable kernel release: Linux 6.18.33, 7.0.10, or 7.1, which incorporate the upstream fix commits (https://git.kernel.org/stable/c/86cf2eba2056bcf9c41fba260e599bd95bf9943b, https://git.kernel.org/stable/c/3042add80c2c50bd127d570b83319af612efde65, https://git.kernel.org/stable/c/478ed6b7d2577439c610f91fa8759a4c878a4264). … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-476 – NULL Pointer Dereference
View allSame technique Denial Of Service
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External POC / Exploit Code
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