net: reject oversized tx_queue_len at netlink parse time

{
  "id": "bfcacb9cd48a5cc76c4d0074192175b6da3ea5400abf48f1830d5c4ec98eeb18",
  "url": "https://osv.dev/vulnerability/CVE-2026-98021",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "net: reject oversized tx_queue_len at netlink parse time",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: net: reject oversized tx_queue_len at netlink parse time rtnl_create_link() assigns IFLA_TXQLEN directly to dev->tx_queue_len without going through netif_change_tx_queue_len(), so a device created with \"ip link add ... txqueuelen 500000\" bypasses the S16_MAX cap and still triggers the oversized ring allocations in pfifo_fast, tun and tap. The veth peer nest (rtnl_nla_parse_ifinfomsg()) and the RTM_NEWLINK-on-existing-device path reach the same sinks. Enforce the cap in ifla_policy instead: IFLA_TXQLEN becomes NLA_POLICY_FULL_RANGE(NLA_U32, &txqlen_range) with txqlen_range = { .min = 0, .max = S16_MAX }. All netlink consumers parse against this policy - rtnl_setlink(), rtnl_newlink() (create and change), and the veth peer nest - so every netlink path is capped at parse time and rejects the attribute with -ERANGE plus a proper \"integer out of range\" extack message before any device state is modified (the RTM_SETLINK half-application wart is gone with it). Document the bound in the rt-link.yaml netlink spec. Conditions to recreate the bug: - CONFIG_NET_SCHED=y, CONFIG_VETH=y, CONFIG_USER_NS=y, CONFIG_NET_NS=y. - Unprivileged user in a fresh user+net namespace (unshare -Urn): ip link add v0 txqueuelen 500000 type veth peer name v1 -> on the fixed kernel this is rejected with -ERANGE (\"integer out of range\" extack) instead of installing an oversized tx_queue_len that later inflates pfifo_fast/tun/tap ring allocati",
    "evidence": "osv:CVE-2026-98021",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.6.160",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.111",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.53",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-98021",
      "aliases": [
        "CVE-2026-98021"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "38f7b870d4a6a5d3ec21557e849620cb7d032965"
                },
                {
                  "fixed": "26ee5f99ffe7ab98e635071290eff14192e9e34a"
                },
                {
                  "fixed": "45ca9f59b6c7ea70e0a17054902b8a556913db34"
                },
                {
                  "fixed": "2fd0880f0272ec022906a05587fd91416ebecc38"
                },
                {
                  "fixed": "a638a2625aa83160a394abe8e8b2e524a80c771b"
                },
                {
                  "fixed": "1aa9e143bf51405665a793d4cc925e1c4f0c5922"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98021.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "2.6.23"
                },
                {
                  "fixed": "6.6.160"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.111"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.53"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.7"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98021.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:48.362468103Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1aa9e143bf51405665a793d4cc925e1c4f0c5922",
        "https://git.kernel.org/stable/c/26ee5f99ffe7ab98e635071290eff14192e9e34a",
        "https://git.kernel.org/stable/c/2fd0880f0272ec022906a05587fd91416ebecc38",
        "https://git.kernel.org/stable/c/45ca9f59b6c7ea70e0a17054902b8a556913db34",
        "https://git.kernel.org/stable/c/a638a2625aa83160a394abe8e8b2e524a80c771b",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98021.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98021",
        "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-2026-98021.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98021",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 516708,
  "published_at": "2026-09-25T10:23:41.505+00:00"
}