Advisory [CVE-2026-64207] fix GSO backlog accounting
This security Red Hat Linux advisory covers CVE-2026-64207.
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Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: dualpi2: fix GSO backlog accounting When DualPI2 splits a GSO skb into N segments, it propagates N additional packets to its parent before returning NET_XMIT_SUCCESS.
The parent then accounts for the original skb once more, leaving its qlen one larger than the number of packets actually queued.
With QFQ as the parent, after all real packets are dequeued, QFQ still has a non-zero qlen while its in-service aggregate has no active classes. qfq_choose_next_agg() returns NULL and qfq_dequeue() passes the result to qfq_peek_skb(), causing a NULL pointer dereference.
Follow the same pattern used by tbf_segment() and taprio: count only successfully queued segments, propagate the difference between the original skb and those segments, and return NET_XMIT_SUCCESS whenever at least one segment was queued. A flaw was found in the Linux kernel's DualPI2 (Dual-rate PI2) queue discipline.
This vulnerability arises from incorrect accounting of Generic Segmentation Offload (GSO) backlog, where the parent queue (such as QFQ - Hierarchical Fair Queueing) miscalculates the number of queued packets.
This miscalculation can lead to a NULL pointer dereference when the system attempts to dequeue packets from an inactive class, resulting in a system crash and a Denial of Service (DoS) condition.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 6 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 6 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 6 days ago·verify at source
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