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net/sched: hhf: clamp quantum in change and init paths

Type: advisorySources: OSV

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

Products
Kernel
Affected versions
Not specified
Fixed versions
5.10.271, 5.15.222, 6.1.189, 6.12.111, 6.18.53, 6.6.158, 7.2.7
CVEs
CVE-2026-98011
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 21:28 UTC · Revision 1

Source evidence

net/sched: hhf: clamp quantum in change and init paths

core-osv · Original source

Published 25 Sept 2026, 10:23 UTC

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

osv:CVE-2026-98011

Kernel

Fixed versions: 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.111, 6.18.53, 7.2.7

Complete source record
{
  "id": "1437748d044a3a2a3e8759d04801ec2746a0fc407c8f62e73b8323a36c239a0e",
  "url": "https://osv.dev/vulnerability/CVE-2026-98011",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "net/sched: hhf: clamp quantum in change and init paths",
    "summary": "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",
    "evidence": "osv:CVE-2026-98011",
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      "modified": "2026-10-28T02:30:39.624382836Z",
      "provider": "osv",
      "references": [
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        "https://git.kernel.org/stable/c/1113b674307ffddd402524bd1fd9d7d5629b705b",
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        "https://git.kernel.org/stable/c/6570f326a6a96bedf3d1d1dab6acc9f8c29104ec",
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        "https://nvd.nist.gov/vuln/detail/CVE-2026-98011",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
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    "related_cves": [
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        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 507242,
  "published_at": "2026-09-25T10:23:35.338+00:00"
}