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CVE-2026-74612

Estado: RecibidaCrítica (10)—

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

veth: fix skb length accounting after XDP frag adjustment

veth exposes non-linear skb fragments through an xdp_buff. If an XDP program adjusts the fragment area, veth_xdp_rcv_skb() copies xdp_frags_size back to skb->data_len but leaves skb->len containing the old fragment contribution.

After a fragment shrink, this makes skb_headlen() larger than the actual linear area. In the reproduced UDP receive path, __skb_datagram_iter() copied 1024 bytes past the actual linear tail to userspace, starting at struct skb_shared_info.

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The copied bytes included the affected skb's nr_frags, xdp_frags_size, and a kernel pointer from skb_shinfo(skb)->frags[0]. Real packet data was displaced by the same amount and truncated at the end.

Subtract the old data_len before replacing it and add the new data_len afterwards, keeping skb->len and skb->data_len synchronized.

Additionally, bpf_xdp_pull_data() can advance data_end while leaving frags present. The skb is then still non-linear, so the old __skb_put(skb, off) triggers SKB_LINEAR_ASSERT().

Use skb_set_tail_pointer() and update skb->len explicitly instead, following bpf_prog_run_generic_xdp(). Unlike __skb_put(), skb_set_tail_pointer() does not require a linear skb.

A 60000-byte UDP datagram on a veth pair with MTU 64000 was shortened by 1024 bytes from its fragment area. Before the fix, all 10 runs produced corrupted payloads. After the fix, all 10 runs matched the expected payload exactly. A forced-tailroom reproducer also exercises bpf_xdp_pull_data() with frags still present; the old code triggers SKB_LINEAR_ASSERT(), while this fix passes 10/10 runs.

CVSS

Probabilidad de explotación (EPSS)

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.

Red sin autenticación (AV:N/PR:N) en kernel Linux. Acceso a memoria del kernel (struct skb_shared_info, punteros) e integridad de datos UDP comprometidas por corrupción de fragmentos XDP.

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 ScanningRestrict File and Directory PermissionsPrivileged Account ManagementRemote Data StorageNetwork SegmentationLimit Access to Resource Over Network

Tecnologías afectadas (1)

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

Linux — Linux KernelAI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-74612",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 10,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 6,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "718a18a0c8a67f97781e40bdef7cdd055c430996",
              "lessThan": "0c3024afabb8064b141f3cedcb1ddd6ab05ad9d5",
              "versionType": "git"
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              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "718a18a0c8a67f97781e40bdef7cdd055c430996",
              "lessThan": "41b96667d42b74bb4b137f1bb78b611a953c5943",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "718a18a0c8a67f97781e40bdef7cdd055c430996",
              "lessThan": "cdf745b7a777f87f51666e5d8f4c6fc279bcf54d",
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            {
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              "lessThan": "3205b0652a37255dbb7ca8f3d942c8d8aa677c21",
              "versionType": "git"
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            {
              "status": "affected",
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              "lessThan": "cb6379feaaff11c4e1e79c26c745ffa23182768a",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "drivers/net/veth.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.18"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "5.18",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.1.184",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "status": "unaffected",
              "version": "6.6.152",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.104",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver",
              "lessThanOrEqual": "7.1.*"
            },
            {
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "drivers/net/veth.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-08-22T16:16:33.770",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/0c3024afabb8064b141f3cedcb1ddd6ab05ad9d5",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/2f2a7f3f8b9f1bffc9b0488aa02b6951b2aec139",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/3205b0652a37255dbb7ca8f3d942c8d8aa677c21",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/41b96667d42b74bb4b137f1bb78b611a953c5943",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/cb6379feaaff11c4e1e79c26c745ffa23182768a",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/cdf745b7a777f87f51666e5d8f4c6fc279bcf54d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nveth: fix skb length accounting after XDP frag adjustment\n\nveth exposes non-linear skb fragments through an xdp_buff. If an XDP\nprogram adjusts the fragment area, veth_xdp_rcv_skb() copies\nxdp_frags_size back to skb->data_len but leaves skb->len containing the\nold fragment contribution.\n\nAfter a fragment shrink, this makes skb_headlen() larger than the actual\nlinear area. In the reproduced UDP receive path, __skb_datagram_iter()\ncopied 1024 bytes past the actual linear tail to userspace, starting at\nstruct skb_shared_info. The copied bytes included the affected skb's\nnr_frags, xdp_frags_size, and a kernel pointer from\nskb_shinfo(skb)->frags[0]. Real packet data was displaced by the same\namount and truncated at the end.\n\nSubtract the old data_len before replacing it and add the new data_len\nafterwards, keeping skb->len and skb->data_len synchronized.\n\nAdditionally, bpf_xdp_pull_data() can advance data_end while leaving\nfrags present. The skb is then still non-linear, so the old\n__skb_put(skb, off) triggers SKB_LINEAR_ASSERT().\n\nUse skb_set_tail_pointer() and update skb->len explicitly instead,\nfollowing bpf_prog_run_generic_xdp(). Unlike __skb_put(),\nskb_set_tail_pointer() does not require a linear skb.\n\nA 60000-byte UDP datagram on a veth pair with MTU 64000 was shortened by\n1024 bytes from its fragment area. Before the fix, all 10 runs produced\ncorrupted payloads. After the fix, all 10 runs matched the expected\npayload exactly. A forced-tailroom reproducer also exercises\nbpf_xdp_pull_data() with frags still present; the old code triggers\nSKB_LINEAR_ASSERT(), while this fix passes 10/10 runs."
    }
  ],
  "lastModified": "2026-08-25T06:18:38.680",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}