CVE-2026-64007

Estado: Pendiente de análisisCrítica (9.8)—

In the Linux kernel, the following vulnerability has been resolved:

netfilter: synproxy: refresh tcphdr after skb_ensure_writable

synproxy_tstamp_adjust() rewrites the TCP timestamp option in place and then patches the TCP checksum via inet_proto_csum_replace4() on the caller-supplied tcphdr pointer. Both ipv4_synproxy_hook() and ipv6_synproxy_hook() obtain that pointer with skb_header_pointer() before calling in, so it may either alias skb->head directly or point at the caller's on-stack _tcph buffer.

Between obtaining the pointer and using it, the function calls skb_ensure_writable(skb, optend), which on a cloned or non-linear skb invokes pskb_expand_head() and frees the old skb->head. After that point the cached th is stale:

Leer descripción completaMostrar menos

The option bytes are written through skb->data and are fine; only the checksum update goes through th and so lands in the wrong place. The result is either a write into freed slab memory or a packet leaving with a checksum that does not match its payload.

Fix by re-deriving th from skb->data + protoff immediately after skb_ensure_writable() succeeds, so the subsequent checksum update targets the linear, writable header.

Detalles técnicos trazas, registros y código del informe original

    caller (ipv[46]_synproxy_hook)
      th = skb_header_pointer(skb, ..., &_tcph)
      synproxy_tstamp_adjust(skb, protoff, th, ...)
        skb_ensure_writable(skb, optend)
          pskb_expand_head()        /* kfree(old skb->head) */
        ...
        inet_proto_csum_replace4(&th->check, ...)
                                    /* writes into freed head, or
                                       into the caller's stack copy
                                       leaving the on-wire checksum
                                       stale */

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 9.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.51%
Percentil entre todas las CVEs puntuadas: 42
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access85 %
Impacto secundarioT1565.002 Transmitted Data Manipulationimpact70 %

Vulnerabilidad remota en netfilter (AV:N, PR:N, UI:N) que permite corrupción de checksum TCP o escritura en memoria liberada; DoS por paquetes malformados o manipulación de datos en tránsito.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Vulnerability Scanning Privileged Account Management Network Segmentation Limit Access to Resource Over Network Filter Network Traffic Encrypt Sensitive Information

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Linux — Linux Kernel^AI

Referencias

JSON original (NVD)

Mostrar

{
  "id": "CVE-2026-64007",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 9.8,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 3.9
      }
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        {
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              "version": "6.1.176",
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            {
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              "version": "6.6.143",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
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            {
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            {
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          ],
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          ],
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        }
      ]
    }
  ],
  "published": "2026-07-19T16:17:40.407",
  "references": [
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      "url": "https://git.kernel.org/stable/c/92170e6afe927ab2792a3f71902845789c8e31b1",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/f0fea2b6d5453a11ad11713bbf37561b9b3a7edf",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Awaiting Analysis",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: synproxy: refresh tcphdr after skb_ensure_writable\n\nsynproxy_tstamp_adjust() rewrites the TCP timestamp option in place\nand then patches the TCP checksum via inet_proto_csum_replace4() on\nthe caller-supplied tcphdr pointer.  Both ipv4_synproxy_hook() and\nipv6_synproxy_hook() obtain that pointer with skb_header_pointer()\nbefore calling in, so it may either alias skb->head directly or\npoint at the caller's on-stack _tcph buffer.\n\nBetween obtaining the pointer and using it, the function calls\nskb_ensure_writable(skb, optend), which on a cloned or non-linear\nskb invokes pskb_expand_head() and frees the old skb->head.  After\nthat point the cached th is stale:\n\n    caller (ipv[46]_synproxy_hook)\n      th = skb_header_pointer(skb, ..., &_tcph)\n      synproxy_tstamp_adjust(skb, protoff, th, ...)\n        skb_ensure_writable(skb, optend)\n          pskb_expand_head()        /* kfree(old skb->head) */\n        ...\n        inet_proto_csum_replace4(&th->check, ...)\n                                    /* writes into freed head, or\n                                       into the caller's stack copy\n                                       leaving the on-wire checksum\n                                       stale */\n\nThe option bytes are written through skb->data and are fine; only\nthe checksum update goes through th and so lands in the wrong\nplace.  The result is either a write into freed slab memory or a\npacket leaving with a checksum that does not match its payload.\n\nFix by re-deriving th from skb->data + protoff immediately after\nskb_ensure_writable() succeeds, so the subsequent checksum update\ntargets the linear, writable header."
    }
  ],
  "lastModified": "2026-07-30T14:51:20.077",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}