{
  "affected": [
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:12",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.1.176-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:13",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.12.94-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "ecosystem_specific": {
        "urgency": "not yet assigned"
      },
      "package": {
        "ecosystem": "Debian:14",
        "name": "linux"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.0.12-1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:  xfrm: Check for underflow in xfrm_state_mtu  Leo Lin reported OOB write issue in esp component:    xfrm_state_mtu() returns u32 but performs its arithmetic in unsigned   modulo-2^32 space using an attacker-influenced \"header_len + authsize +   net_adj\" subtracted from a small \"mtu\" argument. A nobody user can   install an IPv4 ESP tunnel SA with a large authentication key   (XFRMA_ALG_AUTH_TRUNC, e.g. hmac(sha512), 64-byte key, 64-byte trunc),   configure a small interface MTU (68 bytes), and set XFRMA_TFCPAD to a   large value. When a single UDP datagram is then sent through the   tunnel, xfrm_state_mtu() underflows to a near-2^32 value, and   esp_output() consumes it as a signed int via:          padto      = min(x-\u003etfcpad, xfrm_state_mtu(x, mtu_cached))         esp.tfclen = padto - skb-\u003elen   (assigned to int)    esp.tfclen ends up negative (e.g. -207). It is sign-extended to size_t   when passed to memset() inside esp_output_fill_trailer(), producing a   ~16 EB write of zeroes at skb_tail_pointer(skb). KASAN logs it as   \"Write of size 18446744073709551537 at addr ffff888...\".  Check for underflow and return 1. This causes the sendmsg attempt to fail with ENETUNREACH.",
  "id": "DEBIAN-CVE-2026-64009",
  "modified": "2026-09-14T16:47:27.119872331Z",
  "published": "2026-07-19T16:17:40.663Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://security-tracker.debian.org/tracker/CVE-2026-64009"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2026-64009"
  ]
}