net: add xmit recursion limit to tunnel xmit functions

{
  "id": "0a8738c3a164b9919b1c4bdc9205ec89a9bbe85418fe9596c5049796966ba589",
  "url": "https://osv.dev/vulnerability/CVE-2026-23276",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "net: add xmit recursion limit to tunnel xmit functions",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: net: add xmit recursion limit to tunnel xmit functions Tunnel xmit functions (iptunnel_xmit, ip6tunnel_xmit) lack their own recursion limit. When a bond device in broadcast mode has GRE tap interfaces as slaves, and those GRE tunnels route back through the bond, multicast/broadcast traffic triggers infinite recursion between bond_xmit_broadcast() and ip_tunnel_xmit()/ip6_tnl_xmit(), causing kernel stack overflow. The existing XMIT_RECURSION_LIMIT (8) in the no-qdisc path is not sufficient because tunnel recursion involves route lookups and full IP output, consuming much more stack per level. Use a lower limit of 4 (IP_TUNNEL_RECURSION_LIMIT) to prevent overflow. Add recursion detection using dev_xmit_recursion helpers directly in iptunnel_xmit() and ip6tunnel_xmit() to cover all IPv4/IPv6 tunnel paths including UDP encapsulated tunnels (VXLAN, Geneve, etc.). Move dev_xmit_recursion helpers from net/core/dev.h to public header include/linux/netdevice.h so they can be used by tunnel code. BUG: KASAN: stack-out-of-bounds in blake2s.constprop.0+0xe7/0x160 Write of size 32 at addr ffff88810033fed0 by task kworker/0:1/11 Workqueue: mld mld_ifc_work Call Trace: __build_flow_key.constprop.0 (net/ipv4/route.c:515) ip_rt_update_pmtu (net/ipv4/route.c:1073) iptunnel_xmit (net/ipv4/ip_tunnel_core.c:84) ip_tunnel_xmit (net/ipv4/ip_tunnel.c:847) gre_tap_xmit (net/ipv4/ip_gre.c:779) dev_hard_start_xmit (net/core/dev.c:3887)",
    "evidence": "osv:CVE-2026-23276",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.6.160",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.78",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.19",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.9",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-23276",
      "aliases": [
        "CVE-2026-23276"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                {
                  "fixed": "da5f0166cef3d4285ddbb1b638661263fc03ee92"
                },
                {
                  "fixed": "834c4f645726a25fd71ea50cdfb5c135f8f95d85"
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                {
                  "fixed": "8a57deeb256069f262957d8012418559ff66c385"
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                {
                  "fixed": "b56b8d19bd05e2a8338385c770bc2b60590bc81e"
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                  "fixed": "6f1a9140ecda3baba3d945b9a6155af4268aafc4"
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "introduced": "2.6.35.9"
                },
                {
                  "fixed": "2.6.36"
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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          "versions": [
            "v2.6.35.14",
            "v2.6.35.13",
            "v2.6.35.12",
            "v2.6.35.11",
            "v2.6.35.10",
            "v2.6.35.9"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23276.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "2.6.37"
                },
                {
                  "fixed": "6.6.160"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "6.7.0"
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                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.19"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
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              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-23276.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:29.261017555Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/6f1a9140ecda3baba3d945b9a6155af4268aafc4",
        "https://git.kernel.org/stable/c/834c4f645726a25fd71ea50cdfb5c135f8f95d85",
        "https://git.kernel.org/stable/c/8a57deeb256069f262957d8012418559ff66c385",
        "https://git.kernel.org/stable/c/b56b8d19bd05e2a8338385c770bc2b60590bc81e",
        "https://git.kernel.org/stable/c/da5f0166cef3d4285ddbb1b638661263fc03ee92",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23276.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-23276",
        "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/2026/23xxx/CVE-2026-23276.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-23276",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 496320,
  "published_at": "2026-03-20T08:08:56.575+00:00"
}