{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "7801db8aec957fa6610efe0ee26a6c8bc0f1d73b"
            },
            {
              "fixed": "6890e28840bae4f6805e8de981c4ec8e12a4e064"
            },
            {
              "fixed": "feab9261b537df4ebb8350e4779bc185373059fd"
            },
            {
              "fixed": "f594f04268d01c5fdc975f3f51fc219ea2159ac6"
            },
            {
              "fixed": "d7e7e98d23f42a92d9ab7e36302bd96bd9b33b5f"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.16.0"
            },
            {
              "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"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98104.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_u32: fix duplicate handle when node ID pool is exhausted\n\ngen_new_kid() falls back to returning max (htid | 0xFFF) when both\nidr_alloc_u32() ranges are full, instead of reporting an error.\nu32_change() trusts that value and inserts a new knode with a handle\nthat is already live in the hash table, breaking handle uniqueness\nwithin the table's node ID space.\n\nThe handle was never reserved in ht-\u003ehandle_idr, so every later error\npath that does idr_remove(\u0026ht-\u003ehandle_idr, handle) removes the\nreservation of a different, live knode, which is then reused — one\nfailed add compounds into further duplicates.\n\nThe 4095 limit is per (table, bucket) — ht-\u003ehandle_idr is per hash\ntable and the range is derived from htid (bucketid), so a table with\ndivisor 256 can legitimately hold 256*4095 knodes.\n\nThe sibling helper gen_new_htid() has the same silent in-band failure:\nit returns 0 when the tp_c handle pool (1..0x7FF) is full, and\nu32_init() publishes the root hash table with handle 0 without\nchecking.  Two root tables with handle 0 alias in u32_lookup_ht(),\nallowing cross-tcf_proto knode add/lookup/delete.  Add the same\nexhaustion check that the divisor path already has.\n\nReturn an error so u32_change() fails with ENOSPC/ENOMEM when the\nnode ID space is exhausted, and so u32_init() fails with -ENOMEM\nwhen the hash table ID space is exhausted.  The extack message\ndistinguishes pool exhaustion (-ENOSPC) from a transient allocation\nfailure (-ENOMEM).\n\nConditions to recreate the bug:\n- CONFIG_NET_SCHED=y, CONFIG_CLS_U32=y (or =m with module loaded)\n- Create a clsact qdisc on a device, then add 4095 u32 filters with\n  auto-generated handles to fill the node ID space for the root hash\n  table (single bucket). The 4096th auto-handle filter add triggers\n  the duplicate handle (fh 800::fff reused). Reachable at Level 2\n  (unshare -Urn, namespace-local CAP_NET_ADMIN).\n- For gen_new_htid: create 2047 u32 proto entries on the same block\n  to fill the tp_c handle pool, then create one more. The root table\n  gets handle 0 and aliases with other handle-0 root tables.",
  "id": "CVE-2026-98104",
  "modified": "2026-09-27T03:30:37.136553423Z",
  "published": "2026-09-25T10:35:54.544Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6890e28840bae4f6805e8de981c4ec8e12a4e064"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d7e7e98d23f42a92d9ab7e36302bd96bd9b33b5f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f594f04268d01c5fdc975f3f51fc219ea2159ac6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/feab9261b537df4ebb8350e4779bc185373059fd"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98104.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98104"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "summary": "net/sched: cls_u32: fix duplicate handle when node ID pool is exhausted"
}