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CVE-2026-89786

Estado: RecibidaCrítica (9.1)—

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

ext4: fix out-of-bounds read in ext4_read_inline_dir()

ext4_read_inline_dir() can read a dirent header past the end of its inline buffer, triggering a slab-out-of-bounds read during getdents64():

The dirent payload lives in a buffer of exactly inline_size bytes:

but iteration runs in a position space extra_offset bytes larger (extra_size = extra_offset + inline_size) so the synthetic "." and ".." land at their block-dir offsets.

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A dirent is formed at "dir_buf + pos - extra_offset", yet the ext4_check_dir_entry() length argument uses the larger extra_size. A position whose dirent header would extend past extra_size is therefore accepted, and the rescan loop's rec_len probe and ext4_check_dir_entry() dereference de->rec_len before the entry is rejected.

Reject a position whose minimum-size dirent header would not fit within extra_size before forming de, in both the rescan and main loops, and pass inline_size rather than extra_size to ext4_check_dir_entry() so the length check matches the physical buffer.

Detalles técnicos trazas, registros y código del informe original
  BUG: KASAN: slab-out-of-bounds in __ext4_check_dir_entry
  Read of size 2 at addr ffff88800f3dd23c by task exploit/148
   ...
   __ext4_check_dir_entry
   ext4_read_inline_dir
   iterate_dir

	dir_buf = kmalloc(inline_size, GFP_NOFS);

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.

Vulnerabilidad remota en kernel Linux (AV:N, PR:N) permitiendo lectura fuera de límites en getdents64(), causando DoS por KASAN crash e ilegítima lectura de memoria de kernel.

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

Filter Network TrafficVulnerability ScanningPrivileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkApplication Isolation and Sandboxing

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-2026-89786",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 9.1,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.2,
        "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": [
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              "status": "affected",
              "version": "c4d8b0235aa98f8c26bf94d308be3fdd24154572",
              "lessThan": "d1e7c186555ad65554fd2f2b02f5a539aa35ae48",
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          ],
          "programFiles": [
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          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
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              "status": "affected",
              "version": "3.10"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "3.10",
              "versionType": "semver"
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              "version": "5.15.221",
              "versionType": "semver",
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              "version": "6.1.188",
              "versionType": "semver",
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            },
            {
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.110",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver",
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            },
            {
              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver",
              "lessThanOrEqual": "7.2.*"
            },
            {
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "fs/ext4/inline.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-09-16T09:17:09.330",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/1a1dea633b724a1c042dbcdb1fed27f410916688",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/36bf17bb90cdf7a623499b624b05acde4d2feef5",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/5fd20d4e50dd6e460b3ea8e4396f8553d4526f8f",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/6702c7da86d8cdb88d0fc57166286e115ffeb8c0",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/9333cc809f0a89e001b814155a6cb8903a6274df",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/b060861f662d4826dc700a1c3584243bb3474cfe",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/d1e7c186555ad65554fd2f2b02f5a539aa35ae48",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix out-of-bounds read in ext4_read_inline_dir()\n\next4_read_inline_dir() can read a dirent header past the end of its inline\nbuffer, triggering a slab-out-of-bounds read during getdents64():\n\n  BUG: KASAN: slab-out-of-bounds in __ext4_check_dir_entry\n  Read of size 2 at addr ffff88800f3dd23c by task exploit/148\n   ...\n   __ext4_check_dir_entry\n   ext4_read_inline_dir\n   iterate_dir\n\nThe dirent payload lives in a buffer of exactly inline_size bytes:\n\n\tdir_buf = kmalloc(inline_size, GFP_NOFS);\n\nbut iteration runs in a position space extra_offset bytes larger\n(extra_size = extra_offset + inline_size) so the synthetic \".\" and \"..\"\nland at their block-dir offsets. A dirent is formed at \"dir_buf + pos -\nextra_offset\", yet the ext4_check_dir_entry() length argument uses the\nlarger extra_size. A position whose dirent header would extend past\nextra_size is therefore accepted, and the rescan loop's rec_len probe and\next4_check_dir_entry() dereference de->rec_len before the entry is rejected.\n\nReject a position whose minimum-size dirent header would not fit within\nextra_size before forming de, in both the rescan and main loops, and pass\ninline_size rather than extra_size to ext4_check_dir_entry() so the length\ncheck matches the physical buffer."
    }
  ],
  "lastModified": "2026-09-16T15:18:08.860",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}