net/sched: hhf: cap hh_flows_limit at change time

{
  "id": "ec1cde50a301f369590dca7670c0862a62619f06651f1ba70c422a25f2d7dc80",
  "url": "https://osv.dev/vulnerability/CVE-2026-98234",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "net/sched: hhf: cap hh_flows_limit at change time",
    "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.",
    "evidence": "osv:CVE-2026-98234",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.271",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.222",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.189",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.158",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.112",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.54",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.8",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-98234",
      "aliases": [
        "CVE-2026-98234"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "10239edf86f137ce4c39b62ea9575e8053c549a0"
                },
                {
                  "fixed": "7adfd0a42174b85c6bd678858ecd6674f403f336"
                },
                {
                  "fixed": "35fd423a5c5132c6f4321f6c4f0a7b4b90af830c"
                },
                {
                  "fixed": "06d2a101e89063cb0b9b459104db48bdfb0a797d"
                },
                {
                  "fixed": "d8e2f1f0263b7c97b222c06070cccf13e0ab7112"
                },
                {
                  "fixed": "f3f4a5cb4a6e9b1f1f25d34dfc25f836a1601db4"
                },
                {
                  "fixed": "1731ff1d20489afe4cd01b7d16d37f324746ac54"
                },
                {
                  "fixed": "f6547d27ce2093c5627636fb63dd0b7523c466f9"
                },
                {
                  "fixed": "2cef2588c995722a901368def30befeef9ae55c6"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98234.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "3.14.0"
                },
                {
                  "fixed": "5.10.271"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.222"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.189"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.158"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.112"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.54"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.8"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98234.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:33.594894263Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/06d2a101e89063cb0b9b459104db48bdfb0a797d",
        "https://git.kernel.org/stable/c/1731ff1d20489afe4cd01b7d16d37f324746ac54",
        "https://git.kernel.org/stable/c/2cef2588c995722a901368def30befeef9ae55c6",
        "https://git.kernel.org/stable/c/35fd423a5c5132c6f4321f6c4f0a7b4b90af830c",
        "https://git.kernel.org/stable/c/7adfd0a42174b85c6bd678858ecd6674f403f336",
        "https://git.kernel.org/stable/c/d8e2f1f0263b7c97b222c06070cccf13e0ab7112",
        "https://git.kernel.org/stable/c/f3f4a5cb4a6e9b1f1f25d34dfc25f836a1601db4",
        "https://git.kernel.org/stable/c/f6547d27ce2093c5627636fb63dd0b7523c466f9",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98234.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98234",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98234.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98234",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 501032,
  "published_at": "2026-10-06T08:45:07.215+00:00"
}