In the Linux kernel, the following vulnerability has been resolved:
net/sched: hhf: clamp quantum in change and init paths
hhf_change() accepts any quantum from userspace, including 1. 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, ...) in hhf_change() matching fq_codel_change(). Clamp hhf_init() to [256, 1<<20] matching the siblings, and remove the old fallback that only set quantum=256 on overflow.
Conditions to recreate the bug: CONFIG_NET_SCH_HHF=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices).
tc qdisc add dev dummy0 root hhf tc qdisc change dev dummy0 root hhf quantum 1 stab data 32768 size_log 15 cell_log 0
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon_linux_2023 | — | Upgrade bpftool6.18Upgrade kernel6.18-tools-debuginfoUpgrade kernel6.18-modules-extra-commonUpgrade bpftool6.12-debuginfoUpgrade kernel6.12-debuginfo-common-x86_64Upgrade kernel6.12-headersUpgrade perf6.18-debuginfoUpgrade python3-perf6.12Upgrade kernel6.12Upgrade kernel6.12-modules-extra-commonUpgrade kernel6.12-develUpgrade kernel6.18Upgrade kernel6.12-toolsUpgrade kernel-livepatch-6.18.54-121.166Upgrade kernel6.12-debuginfo-common-aarch64Upgrade kernel6.18-debuginfo-common-aarch64Upgrade kernel6.12-modules-extraUpgrade kernel6.12-tools-develUpgrade python3-perf6.18-debuginfoUpgrade kernel6.18-develUpgrade kernel6.18-headersUpgrade perf6.18Upgrade kernel6.18-tools-develUpgrade kernel6.12-debuginfoUpgrade python3-perf6.12-debuginfoUpgrade kernel6.18-toolsUpgrade kernel6.18-modules-extraUpgrade perf6.12Upgrade microvm-kernel6.18Upgrade bpftool6.12Upgrade kernel-livepatch-6.12.111-136.204Upgrade perf6.12-debuginfoUpgrade bpftool6.18-debuginfoUpgrade kernel6.12-tools-debuginfoUpgrade kernel6.18-debuginfo-common-x86_64Upgrade kernel6.18-debuginfoUpgrade python3-perf6.18 | Oct 13, 2026 | Sep 25, 2026 |
| Debian | — | Upgrade linux-6.12Upgrade linux | Sep 30, 2026 | Sep 25, 2026 |
| Redhat_linux | — | No solution exists | Sep 30, 2026 | Sep 25, 2026 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Oct 13, 2026 | Sep 25, 2026 |
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