CVE-2026-98234 (GCVE-0-2026-98234)
Vulnerability from cvelistv5
Published
2026-10-06 08:45
Modified
2026-10-19 09:16
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: hhf: cap hh_flows_limit at change time hhf_change() stores TCA_HHF_HH_FLOWS_LIMIT with no upper bound. A huge hh_flows_limit lets each new heavy-hitter flow pass the hh_flows_current_cnt check in alloc_new_hh() and forces a fixed-size kzalloc(GFP_ATOMIC) per flow under spoofed traffic, for unbounded memory growth. Bound the attribute with NLA_POLICY_MAX() at 2*HH_FLOWS_CNT (the hhf_init() default) and report the rejected value via extack. The deprecated nested parse is kept: legacy tc does not set NLA_F_NESTED on TCA_OPTIONS. Configs relying on hh_limit above the default were relying on unbounded, unsafe behaviour and are not supported going forward. hhf_init() also ran hhf_change() before setting the default hh_flows_limit, so a user-supplied hh_limit at add time was clobbered back to 2048. Set the default before hhf_change() so the configured value sticks. This is a follow-up to commit eb56a495f59b ("net/sched: hhf: clamp quantum in change and init paths"), which bounded the quantum of the same qdisc; the hh_flows_limit bound is the remaining unbounded knob of that series' scope. Conditions to recreate the bug: CAP_NET_ADMIN in a user namespace; tc qdisc change dev X root hhf hh_limit 4294967295 succeeds and the value is echoed by tc qdisc show, unbounding heavy-hitter flow allocations; also tc qdisc add dev X root hhf hh_limit 500 stores 2048 instead of 500.
References
Impacted products
Vendor Product Version
Linux Linux Version: 10239edf86f137ce4c39b62ea9575e8053c549a0
Version: 10239edf86f137ce4c39b62ea9575e8053c549a0
Version: 10239edf86f137ce4c39b62ea9575e8053c549a0
Version: 10239edf86f137ce4c39b62ea9575e8053c549a0
Version: 10239edf86f137ce4c39b62ea9575e8053c549a0
Version: 10239edf86f137ce4c39b62ea9575e8053c549a0
Version: 10239edf86f137ce4c39b62ea9575e8053c549a0
Version: 10239edf86f137ce4c39b62ea9575e8053c549a0
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{
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          "product": "Linux",
          "programFiles": [
            "net/sched/sch_hhf.c"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: hhf: cap hh_flows_limit at change time\n\nhhf_change() stores TCA_HHF_HH_FLOWS_LIMIT with no upper bound. A huge\nhh_flows_limit lets each new heavy-hitter flow pass the\nhh_flows_current_cnt check in alloc_new_hh() and forces a fixed-size\nkzalloc(GFP_ATOMIC) per flow under spoofed traffic, for unbounded memory\ngrowth.\n\nBound the attribute with NLA_POLICY_MAX() at 2*HH_FLOWS_CNT (the\nhhf_init() default) and report the rejected value via extack. The\ndeprecated nested parse is kept: legacy tc does not set NLA_F_NESTED on\nTCA_OPTIONS. Configs relying on hh_limit above the default were relying\non unbounded, unsafe behaviour and are not supported going forward.\n\nhhf_init() also ran hhf_change() before setting the default\nhh_flows_limit, so a user-supplied hh_limit at add time was clobbered\nback to 2048. Set the default before hhf_change() so the configured\nvalue sticks.\n\nThis is a follow-up to commit eb56a495f59b (\"net/sched: hhf: clamp\nquantum in change and init paths\"), which bounded the quantum of the\nsame qdisc; the hh_flows_limit bound is the remaining unbounded knob of\nthat series\u0027 scope.\n\nConditions to recreate the bug: CAP_NET_ADMIN in a user namespace;\ntc qdisc change dev X root hhf hh_limit 4294967295 succeeds and the\nvalue is echoed by tc qdisc show, unbounding heavy-hitter flow\nallocations; also tc qdisc add dev X root hhf hh_limit 500 stores 2048\ninstead of 500."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:16:06.128Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/7adfd0a42174b85c6bd678858ecd6674f403f336"
        },
        {
          "url": "https://git.kernel.org/stable/c/35fd423a5c5132c6f4321f6c4f0a7b4b90af830c"
        },
        {
          "url": "https://git.kernel.org/stable/c/06d2a101e89063cb0b9b459104db48bdfb0a797d"
        },
        {
          "url": "https://git.kernel.org/stable/c/d8e2f1f0263b7c97b222c06070cccf13e0ab7112"
        },
        {
          "url": "https://git.kernel.org/stable/c/f3f4a5cb4a6e9b1f1f25d34dfc25f836a1601db4"
        },
        {
          "url": "https://git.kernel.org/stable/c/1731ff1d20489afe4cd01b7d16d37f324746ac54"
        },
        {
          "url": "https://git.kernel.org/stable/c/f6547d27ce2093c5627636fb63dd0b7523c466f9"
        },
        {
          "url": "https://git.kernel.org/stable/c/2cef2588c995722a901368def30befeef9ae55c6"
        }
      ],
      "title": "net/sched: hhf: cap hh_flows_limit at change time",
      "x_generator": {
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98234",
    "datePublished": "2026-10-06T08:45:07.215Z",
    "dateReserved": "2026-09-25T10:25:14.329Z",
    "dateUpdated": "2026-10-19T09:16:06.128Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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