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CVE-2026-72108

Estado: RecibidaAlta (7.8)—

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

dm thin metadata: fix metadata snapshot consistency on commit failure

__reserve_metadata_snap() and __release_metadata_snap() modify the superblock's held_root directly in the block_manager's buffer. If the subsequent metadata commit fails, the held_root gets flushed to disk through the abort_transaction path, resulting in inconsistent metadata.

Reproducer 1: __reserve_metadata_snap()

dmsetup create tmeta --table "0 112 linear /dev/sdc 0 112 3984 error"

2. Create a 16 MiB thin-pool

dmsetup create tdata --table "0 32768 zero" dd if=/dev/zero of=/dev/mapper/tmeta bs=4k count=1 dmsetup create tpool --table "0 32768 thin-pool /dev/mapper/tmeta \ /dev/mapper/tdata 128 0 1 skip_block_zeroing"

Leer descripción completaMostrar menos

dmsetup message tpool 0 "reserve_metadata_snap"

thin_check v1.2.2 result:

Bad reference count for metadata block 6. Expected 2, but space map contains 1. Bad reference count for metadata block 7. Expected 2, but space map contains 1. Bad reference count for metadata block 13. Expected 1, but space map contains 0.

Reproducer 2: __release_metadata_snap()

dmsetup create tmeta --table "0 128 linear /dev/sdc 0 128 3968 error"

2. Create a 16 MiB thin-pool

dmsetup create tdata --table "0 32768 zero" dd if=/dev/zero of=/dev/mapper/tmeta bs=4k count=1 dmsetup create tpool --table "0 32768 thin-pool /dev/mapper/tmeta \ /dev/mapper/tdata 128 0 1 skip_block_zeroing"

dmsetup message tpool 0 "reserve_metadata_snap" dmsetup message tpool 0 "release_metadata_snap"

thin_check v1.2.2 result:

Bad reference count for metadata block 6. Expected 1, but space map contains 2. Bad reference count for metadata block 7. Expected 1, but space map contains 2. 1 metadata blocks have leaked.

Fix by deferring the held_root update to commit time.

Additionally, move the existing-snapshot check in __reserve_metadata_snap before the shadow operation to avoid unnecessary work. In __release_metadata_snap, clear pmd->held_root before btree deletion so partial failure leaks blocks rather than leaving a stale reference, and unlock the snapshot block before decrementing its refcount.

Detalles técnicos trazas, registros y código del informe original
1. Create a 2 MiB metadata device and make the region after the 14th
   block inaccessible, to trigger metadata commit failure in the
   subsequent reserve_metadata_snap operation. The 14th block will be
   the shadow destination for the index block.

3. Take a metadata snapshot to trigger metadata commit failure and
   transaction abort. However, the held_root is written to disk,
   breaking metadata consistency.

1. Create a 2 MiB metadata device and make the region after the 16th
   block inaccessible, to trigger metadata commit failure in the
   subsequent release_metadata_snap operation. The 16th block will be
   the shadow destination for the index block.

3. Reserve then release the metadata snapshot, to trigger metadata
   commit failure and transaction abort. The held_root gets removed
   from the on-disk superblock, causing inconsistent metadata.

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 local (AV:L, PR:L) sin interacción del usuario que permite a un atacante con privilegios locales corromper metadatos del kernel (impacto de integridad de datos) y causar inconsistencias que pueden llevar a denegación de servicio.

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

Threat Intelligence ProgramRestrict File and Directory PermissionsRemote Data StorageFilter Network TrafficExecution PreventionEncrypt 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 KernelAI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-72108",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
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          "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": "991d9fa02da0dd1f843dc011376965e0c8c6c9b5",
              "lessThan": "4af993468193cf4cd32ba5748786e7801945f7d2",
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              "versionType": "git"
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              "lessThan": "b5f9a31c51cbb374a1713c3494f8660ab070f035",
              "versionType": "git"
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            {
              "status": "affected",
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              "lessThan": "7f76245960a332f39b08cc556e675d1765dc5bbb",
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            {
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          ],
          "programFiles": [
            "drivers/md/dm-thin-metadata.c"
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          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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          "versions": [
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            {
              "status": "unaffected",
              "version": "0",
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              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.10.261",
              "versionType": "semver",
              "lessThanOrEqual": "5.10.*"
            },
            {
              "status": "unaffected",
              "version": "5.15.212",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "status": "unaffected",
              "version": "6.1.178",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "status": "unaffected",
              "version": "6.6.145",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.97",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.18.40",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver",
              "lessThanOrEqual": "7.1.*"
            },
            {
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "drivers/md/dm-thin-metadata.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-08-15T06:21:25.047",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/3dc9ae1029320d77472c44965e572f176949cd63",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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    {
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/9f1a0d27586ceab055e6b050e3731ce3c6b2c4f0",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/abf2fae92cbe68945028987d498cc72f8f0e23a8",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/b5f9a31c51cbb374a1713c3494f8660ab070f035",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndm thin metadata: fix metadata snapshot consistency on commit failure\n\n__reserve_metadata_snap() and __release_metadata_snap() modify the\nsuperblock's held_root directly in the block_manager's buffer. If the\nsubsequent metadata commit fails, the held_root gets flushed to disk\nthrough the abort_transaction path, resulting in inconsistent metadata.\n\nReproducer 1: __reserve_metadata_snap()\n\n1. Create a 2 MiB metadata device and make the region after the 14th\n   block inaccessible, to trigger metadata commit failure in the\n   subsequent reserve_metadata_snap operation. The 14th block will be\n   the shadow destination for the index block.\n\ndmsetup create tmeta --table \"0 112 linear /dev/sdc 0\n112 3984 error\"\n\n2. Create a 16 MiB thin-pool\n\ndmsetup create tdata --table \"0 32768 zero\"\ndd if=/dev/zero of=/dev/mapper/tmeta bs=4k count=1\ndmsetup create tpool --table \"0 32768 thin-pool /dev/mapper/tmeta \\\n/dev/mapper/tdata 128 0 1 skip_block_zeroing\"\n\n3. Take a metadata snapshot to trigger metadata commit failure and\n   transaction abort. However, the held_root is written to disk,\n   breaking metadata consistency.\n\ndmsetup message tpool 0 \"reserve_metadata_snap\"\n\nthin_check v1.2.2 result:\n\nBad reference count for metadata block 6.  Expected 2, but space map contains 1.\nBad reference count for metadata block 7.  Expected 2, but space map contains 1.\nBad reference count for metadata block 13.  Expected 1, but space map contains 0.\n\nReproducer 2: __release_metadata_snap()\n\n1. Create a 2 MiB metadata device and make the region after the 16th\n   block inaccessible, to trigger metadata commit failure in the\n   subsequent release_metadata_snap operation. The 16th block will be\n   the shadow destination for the index block.\n\ndmsetup create tmeta --table \"0 128 linear /dev/sdc 0\n128 3968 error\"\n\n2. Create a 16 MiB thin-pool\n\ndmsetup create tdata --table \"0 32768 zero\"\ndd if=/dev/zero of=/dev/mapper/tmeta bs=4k count=1\ndmsetup create tpool --table \"0 32768 thin-pool /dev/mapper/tmeta \\\n/dev/mapper/tdata 128 0 1 skip_block_zeroing\"\n\n3. Reserve then release the metadata snapshot, to trigger metadata\n   commit failure and transaction abort. The held_root gets removed\n   from the on-disk superblock, causing inconsistent metadata.\n\ndmsetup message tpool 0 \"reserve_metadata_snap\"\ndmsetup message tpool 0 \"release_metadata_snap\"\n\nthin_check v1.2.2 result:\n\nBad reference count for metadata block 6.  Expected 1, but space map contains 2.\nBad reference count for metadata block 7.  Expected 1, but space map contains 2.\n1 metadata blocks have leaked.\n\nFix by deferring the held_root update to commit time.\n\nAdditionally, move the existing-snapshot check in __reserve_metadata_snap\nbefore the shadow operation to avoid unnecessary work. In\n__release_metadata_snap, clear pmd->held_root before btree deletion so\npartial failure leaks blocks rather than leaving a stale reference, and\nunlock the snapshot block before decrementing its refcount."
    }
  ],
  "lastModified": "2026-08-17T06:18:09.860",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}