CVE-2026-98021 (GCVE-0-2026-98021)
Vulnerability from cvelistv5
Published
2026-09-25 10:23
Modified
2026-10-21 12:54
Severity ?
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 allocations. - ip link set v0 txqueuelen 500000 is likewise rejected at parse time.
References
Impacted products
Vendor Product Version
Linux Linux Version: 38f7b870d4a6a5d3ec21557e849620cb7d032965
Version: 38f7b870d4a6a5d3ec21557e849620cb7d032965
Version: 38f7b870d4a6a5d3ec21557e849620cb7d032965
Version: 38f7b870d4a6a5d3ec21557e849620cb7d032965
Version: 38f7b870d4a6a5d3ec21557e849620cb7d032965
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{
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          "programFiles": [
            "Documentation/netlink/specs/rt-link.yaml",
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              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: reject oversized tx_queue_len at netlink parse time\n\nrtnl_create_link() assigns IFLA_TXQLEN directly to dev-\u003etx_queue_len\nwithout going through netif_change_tx_queue_len(), so a device created\nwith \"ip link add ... txqueuelen 500000\" bypasses the S16_MAX cap and\nstill triggers the oversized ring allocations in pfifo_fast, tun and\ntap. The veth peer nest (rtnl_nla_parse_ifinfomsg()) and the\nRTM_NEWLINK-on-existing-device path reach the same sinks.\n\nEnforce the cap in ifla_policy instead: IFLA_TXQLEN becomes\nNLA_POLICY_FULL_RANGE(NLA_U32, \u0026txqlen_range) with\ntxqlen_range = { .min = 0, .max = S16_MAX }. All netlink consumers\nparse against this policy - rtnl_setlink(), rtnl_newlink() (create\nand change), and the veth peer nest - so every netlink path is capped\nat parse time and rejects the attribute with -ERANGE plus a proper\n\"integer out of range\" extack message before any device state is\nmodified (the RTM_SETLINK half-application wart is gone with it).\n\nDocument the bound in the rt-link.yaml netlink spec.\n\nConditions to recreate the bug:\n- CONFIG_NET_SCHED=y, CONFIG_VETH=y, CONFIG_USER_NS=y, CONFIG_NET_NS=y.\n- Unprivileged user in a fresh user+net namespace (unshare -Urn):\n  ip link add v0 txqueuelen 500000 type veth peer name v1\n  -\u003e on the fixed kernel this is rejected with -ERANGE (\"integer out\n  of range\" extack) instead of installing an oversized tx_queue_len\n  that later inflates pfifo_fast/tun/tap ring allocations.\n- ip link set v0 txqueuelen 500000 is likewise rejected at parse time."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:54:05.196Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/26ee5f99ffe7ab98e635071290eff14192e9e34a"
        },
        {
          "url": "https://git.kernel.org/stable/c/45ca9f59b6c7ea70e0a17054902b8a556913db34"
        },
        {
          "url": "https://git.kernel.org/stable/c/2fd0880f0272ec022906a05587fd91416ebecc38"
        },
        {
          "url": "https://git.kernel.org/stable/c/a638a2625aa83160a394abe8e8b2e524a80c771b"
        },
        {
          "url": "https://git.kernel.org/stable/c/1aa9e143bf51405665a793d4cc925e1c4f0c5922"
        }
      ],
      "title": "net: reject oversized tx_queue_len at netlink parse time",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98021",
    "datePublished": "2026-09-25T10:23:41.505Z",
    "dateReserved": "2026-09-25T10:19:56.069Z",
    "dateUpdated": "2026-10-21T12:54:05.196Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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