{
  "affected": [
    {
      "ranges": [
        {
          "events": [
            {
              "introduced": "daba287b299ec7a2c61ae3a714920e90e8396ad5"
            },
            {
              "fixed": "83fedc4741210f75be8ca5b487985a242bf6f18d"
            },
            {
              "fixed": "81f540827d243b8dad76c1f44e70ea31719f393c"
            },
            {
              "fixed": "b83641e0ab8b20eefcc4cdc5a059f897375291a2"
            }
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "type": "GIT"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Linux",
        "name": "Kernel"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.13.0"
            },
            {
              "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-2026-98393.json"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv4: Fix UDP length overflow with PMTU discover and big MTU\n\nThis commit bounds cork-\u003ebase.fragsize to IP_MAX_MTU to avoid a\npossible overflow of UDP length that triggers a WARN in\nudp_set_len_short when setsockopt IP_MTU_DISCOVER is set to\nIP_PMTUDISC_PROBE, and a large packet is sent over a netdev with an\nunusually large MTU.\n\nSteps to reproduce:\n\n1. Set device MTU bigger than IP_MAX_MTU + 20. cork-\u003ebase.fragsize will\n   be set to that MTU in ip_setup_cork.\n2. Set IP_MTU_DISCOVER to IP_PMTUDISC_PROBE. It lets maxnonfragsize be\n   set to device MTU (cork-\u003efragsize) in __ip_append_data, rather than\n   to IP_MAX_MTU.\n3. Send 65528 bytes of payload (+8 bytes of UDP header, +20 bytes of\n   IPv4 header). Device MTU allows it (it's only one byte bigger than\n   IP_MAX_MTU + IPv4 header, and the device MTU is bigger than that).\n4. The UDP length in the built packet is 65536, which overflows the\n   16-bit length field and triggers the WARN in udp_set_len_short.\n\nNote: IP_PMTUDISC_DO with IPv4 is safe, because ip_dst_mtu_maybe_forward\nalways clamps at IP_MAX_MTU, unlike ip6_dst_mtu_maybe_forward.\n\nThe Fixes tag points at the first commit where I could reproduce the\noverflow with IPv4 and IP_PMTUDISC_PROBE.",
  "id": "CVE-2026-98393",
  "modified": "2026-10-15T02:31:13.269134027Z",
  "published": "2026-10-14T13:25:56.697Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/81f540827d243b8dad76c1f44e70ea31719f393c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/83fedc4741210f75be8ca5b487985a242bf6f18d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b83641e0ab8b20eefcc4cdc5a059f897375291a2"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98393.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98393"
    }
  ],
  "schema_version": "1.9.0",
  "summary": "net: ipv4: Fix UDP length overflow with PMTU discover and big MTU"
}