{
  "schemaVersion": 1,
  "attribution": [
    {
      "source": "CISA Known Exploited Vulnerabilities",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "licence": "US government work"
    },
    {
      "source": "GitHub Advisory Database",
      "url": "https://github.com/advisories",
      "licence": "CC BY 4.0"
    },
    {
      "source": "Have I Been Pwned",
      "url": "https://haveibeenpwned.com/",
      "licence": "CC BY 4.0"
    },
    {
      "source": "CVE Program (CVE records)",
      "url": "https://www.cve.org/Legal/TermsOfUse",
      "licence": "CVE Terms of Use",
      "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.",
      "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss/",
      "licence": "free to use; FIRST requests attribution"
    }
  ],
  "record": {
    "id": "CVE-2026-64009",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-64009",
    "idYear": 2026,
    "status": "PUBLISHED",
    "publishedAt": "2026-07-19T14:56:24.448Z",
    "updatedAt": "2026-10-19T20:28:08.230Z",
    "importedAt": "2026-10-24T01:58:25.636Z",
    "snapshot": {
      "id": "cve_2026-10-24_midnight_baseline",
      "at": "2026-10-24T00:00:00.000Z",
      "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"
    },
    "facts": {
      "title": "xfrm: Check for underflow in xfrm_state_mtu",
      "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: Check for underflow in xfrm_state_mtu\n\nLeo Lin reported OOB write issue in esp component:\n\n  xfrm_state_mtu() returns u32 but performs its arithmetic in unsigned\n  modulo-2^32 space using an attacker-influenced \"header_len + authsize +\n  net_adj\" subtracted from a small \"mtu\" argument. A nobody user can\n  install an IPv4 ESP tunnel SA with a large authentication key\n  (XFRMA_ALG_AUTH_TRUNC, e.g. hmac(sha512), 64-byte key, 64-byte trunc),\n  configure a small interface MTU (68 bytes), and set XFRMA_TFCPAD to a\n  large value. When a single UDP datagram is then sent through the\n  tunnel, xfrm_state_mtu() underflows to a near-2^32 value, and\n  esp_output() consumes it as a signed int via:\n\n        padto      = min(x->tfcpad, xfrm_state_mtu(x, mtu_cached))\n        esp.tfclen = padto - skb->len   (assigned to int)\n\n  esp.tfclen ends up negative (e.g. -207). It is sign-extended to size_t\n  when passed to memset() inside esp_output_fill_trailer(), producing a\n  ~16 EB write of zeroes at skb_tail_pointer(skb). KASAN logs it as\n  \"Write of size 18446744073709551537 at addr ffff888...\".\n\nCheck for underflow and return 1. This causes the sendmsg attempt to\nfail with ENETUNREACH.",
      "affected": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "c5c2523893747f88a83376abad310c8ad13f7197",
              "status": "affected",
              "versionType": "git",
              "lessThan": "8014f70c4e6e5ab101ae3860a614e65e988372e3"
            },
            {
              "version": "c5c2523893747f88a83376abad310c8ad13f7197",
              "status": "affected",
              "versionType": "git",
              "lessThan": "1021d2877b689a648b27815c854557a917122e93"
            },
            {
              "version": "c5c2523893747f88a83376abad310c8ad13f7197",
              "status": "affected",
              "versionType": "git",
              "lessThan": "2a41b1b31c61c52b972278ce1732a1443f5e89ed"
            },
            {
              "version": "c5c2523893747f88a83376abad310c8ad13f7197",
              "status": "affected",
              "versionType": "git",
              "lessThan": "fccd685b32df5aaf6bad4381eeda216468e283f0"
            },
            {
              "version": "c5c2523893747f88a83376abad310c8ad13f7197",
              "status": "affected",
              "versionType": "git",
              "lessThan": "820e501be8aee4b365d218d83227b314309c5fda"
            },
            {
              "version": "c5c2523893747f88a83376abad310c8ad13f7197",
              "status": "affected",
              "versionType": "git",
              "lessThan": "82ac903e0b519849647657b8c48d21237ada06a2"
            },
            {
              "version": "c5c2523893747f88a83376abad310c8ad13f7197",
              "status": "affected",
              "versionType": "git",
              "lessThan": "3db50ceeacb52806d8fe86fb1dfe944df0b9f789"
            },
            {
              "version": "c5c2523893747f88a83376abad310c8ad13f7197",
              "status": "affected",
              "versionType": "git",
              "lessThan": "742b04d0550b0ec89dcbc99537ec88653bd1ad90"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "versions": [
            {
              "version": "2.6.22",
              "status": "affected"
            },
            {
              "version": "0",
              "status": "unaffected",
              "versionType": "semver",
              "lessThan": "2.6.22"
            },
            {
              "version": "5.10.259",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.10.*"
            },
            {
              "version": "5.15.210",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "version": "6.1.176",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "version": "6.6.143",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "version": "6.12.93",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "version": "6.18.35",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "version": "7.0.12",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "7.0.*"
            },
            {
              "version": "7.1",
              "status": "unaffected",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ]
        }
      ]
    }
  }
}