CVE-2026-98012

In the Linux kernel, the following vulnerability has been resolved:

net/sched: sfq: clamp quantum in change path

sfq change() accepts any non-negative quantum (only rejects (int)ctl->quantum < 0). With a crafted size table qdisc pkt len reaches ~2 GiB, so quantum=1 makes the deficit-refill loop spin ~2^31 times under the qdisc lock (a soft lockup / denial of service).

Add max(256U, ...) matching fq codel change(). Reject quantum > 1<<20 with -EINVAL, matching fq codel change() and the init clamp.

Conditions to recreate the bug: CONFIG NET SCH SFQ=y. Requires CAP NET ADMIN (namespace-local via unshare -Urn suffices).

tc qdisc add dev dummy0 root sfq tc qdisc change dev dummy0 root sfq quantum 1 stab data 32768 size log 15 cell log 0