CVE-2026-64530

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle tcf_classify() can return TC_ACT_CONSUMED while the skb is held by the defragmentation engine (e.g. act_ct on out-of-order fragments). When that happens the skb is no longer owned by the caller and must not be touched again. tcf_qevent_handle() did not handle TC_ACT_CONSUMED: it fell through the switch and returned the skb to the caller as if classification had passed. The only qdisc that wires up qevents today is RED, via three call sites (qe_mark on RED_PROB_MARK/HARD_MARK, qe_early_drop on congestion_drop) red_enqueue() was continuing to operate on an skb it no longer owns in this case -- enqueueing it, dropping it, or updating statistics. Resulting in a UAF. tc qdisc add dev eth0 root handle 1: red ... qevent early_drop block 10 tc filter add block 10 ... action ct (with ct defrag enabled and traffic that produces out-of-order fragments, e.g. a fragmented UDP stream) Handle TC_ACT_CONSUMED in tcf_qevent_handle() the same way the ingress and egress fast paths do: treat it as stolen and return NULL without touching the skb. Unlike the TC_ACT_STOLEN case, the skb must not be dropped/freed here, as it is no longer owned by us.

CVSS 3.1 breakdown

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

• https://git.kernel.org/stable/c/2140c2f3f2e7b066e1ae616ede8856cafd8015e9
• https://git.kernel.org/stable/c/447d493034a9cf7bf13a2abac86d0573d907ec2f
• https://git.kernel.org/stable/c/5ed3d6f85991656667059d3fa5a1d683ac58c447
• https://git.kernel.org/stable/c/a8a02897f2b479127db261de05cbf0c28b98d159
• https://git.kernel.org/stable/c/e1270e69dcf2c3512c453484178f2e9dc0db3f05
• https://git.kernel.org/stable/c/e28aedab9488343924d227b5a896faed67ce84d5
• https://git.kernel.org/stable/c/f42e8134a3a1074b834a574d404352f867ba994a

Frequently asked