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CVE-2026-72211 (GCVE-0-2026-72211)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:54 – Updated: 2026-08-18 06:56
VLAI
Title
ntfs: grow index root value before reparent header update
Summary
In the Linux kernel, the following vulnerability has been resolved: ntfs: grow index root value before reparent header update ntfs_ir_reparent() moves the resident index root entries into an index block and leaves a small root stub containing the child VCN. That root stub can be larger than the existing resident value. For example, an empty root with value_length 48 has an index area of 32 bytes, while the large-index root stub needs index_length and allocated_size of 40 bytes. The current code publishes the larger index.index_length and index.allocated_size before resizing the resident value. If the resize returns -ENOSPC, the recovery path can call ntfs_inode_add_attrlist(), which looks attributes up again while the root header says allocated_size 40 but the resident value still only provides 32 bytes of index area. Lookup-time $INDEX_ROOT validation then correctly rejects that transient layout as corrupt. This reproduces as a generic/013 failure under qemu. In the failing run, the transient root had value_len=48, index_size=32, index_length=40, and allocated_size=40, and ntfsprogs-plus ntfsck reported "Corrupt index root in MFT record 1177". When the root stub grows, resize the resident value before publishing the larger root header. If the resize fails, the old root remains valid for recovery lookups. Keep the existing header-before-resize ordering for shrink or same-size cases so the resident value never temporarily exposes an allocated_size beyond its bounds.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 0a8ac0c1fa0b99a5b29002bc7f232ed7eafddef0 , < 38d444271604afc6381ddb5a181e391915c35fae (git)
Affected: 0a8ac0c1fa0b99a5b29002bc7f232ed7eafddef0 , < 0bb508fb3b97e4802ec727fd2af4d608f65dd190 (git)
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Linux Linux Affected: 7.1
Unaffected: 0 , < 7.1 (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ntfs/index.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.5",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "7.2",
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nntfs: grow index root value before reparent header update\n\nntfs_ir_reparent() moves the resident index root entries into an index\nblock and leaves a small root stub containing the child VCN. That root\nstub can be larger than the existing resident value. For example, an\nempty root with value_length 48 has an index area of 32 bytes, while the\nlarge-index root stub needs index_length and allocated_size of 40 bytes.\n\nThe current code publishes the larger index.index_length and\nindex.allocated_size before resizing the resident value. If the resize\nreturns -ENOSPC, the recovery path can call ntfs_inode_add_attrlist(),\nwhich looks attributes up again while the root header says\nallocated_size 40 but the resident value still only provides 32 bytes of\nindex area. Lookup-time $INDEX_ROOT validation then correctly rejects\nthat transient layout as corrupt.\n\nThis reproduces as a generic/013 failure under qemu. In the failing run,\nthe transient root had value_len=48, index_size=32, index_length=40, and\nallocated_size=40, and ntfsprogs-plus ntfsck reported \"Corrupt index\nroot in MFT record 1177\".\n\nWhen the root stub grows, resize the resident value before publishing the\nlarger root header. If the resize fails, the old root remains valid for\nrecovery lookups. Keep the existing header-before-resize ordering for\nshrink or same-size cases so the resident value never temporarily\nexposes an allocated_size beyond its bounds."
        }
      ],
      "metrics": [
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          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - ntfs_ir_reparent is reached via ntfs_index_add_filename on VFS create/mkdir/link/rename; the ntfs driver registers ntfs_export_ops, so remote NFS or ksmbd clients writing to an exported rw NTFS share can trigger index reparent without local shell access.\nAC:L - An attacker can deterministically fill a directory and pack the host MFT record so index-root reparent needs a larger stub than the resident value_length, forcing -ENOSPC on resize; xfstests generic/013 reproduces this without races or victim-specific timing.\nPR:N - Exploitation requires only permission to create or link files in an NTFS directory (local user with write access, authenticated SMB/NFS client, or guest/anonymous write on a misconfigured export); mounting is environmental setup, not a privilege needed during the trigger.\nUI:N - Once an administrator has rw-mounted and optionally exported the NTFS volume, the attacker drives file-creation or link operations that grow the directory index; no further victim clicks, opens, or cooperative actions are required beyond that standing configuration.\nS:U - Impact is confined to on-disk NTFS $INDEX_ROOT metadata corruption and operation failure within the host kernel/filesystem security authority; this is standard local or network filesystem exploitation, not a VM escape or cross-authority sandbox breakout.\nC:H - Publishing allocated_size beyond the resident value index area leaves a transient header/buffer mismatch in the mapped MFT record; recovery lookups and subsequent index walks can read past the resident value bounds, and persistent corrupt $INDEX_ROOT can expose adjacent directory/MFT metadata.\nI:H - Failed reparent can leave $INDEX_ROOT with index_length and allocated_size larger than the resident value (ntfsck reports Corrupt index root in MFT record), enabling attacker-steerable on-disk directory index metadata corruption beyond the intended filesystem state.\nA:H - Recovery fails when $INDEX_ROOT validation rejects the inconsistent root, aborting directory updates and leaving corrupt on-disk index metadata that can render directories unusable; this was reproduced as an xfstests generic/013 failure with persistent filesystem corruption."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-18T06:56:30.876Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/38d444271604afc6381ddb5a181e391915c35fae"
        },
        {
          "url": "https://git.kernel.org/stable/c/0bb508fb3b97e4802ec727fd2af4d608f65dd190"
        }
      ],
      "title": "ntfs: grow index root value before reparent header update",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72211",
    "datePublished": "2026-08-15T05:54:06.292Z",
    "dateReserved": "2026-08-09T03:40:39.912Z",
    "dateUpdated": "2026-08-18T06:56:30.876Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-72211",
      "date": "2026-09-04",
      "epss": "0.00516",
      "percentile": "0.42022"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-72211\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-08-15T06:21:39.803\",\"lastModified\":\"2026-08-18T07:16:54.370\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nntfs: grow index root value before reparent header update\\n\\nntfs_ir_reparent() moves the resident index root entries into an index\\nblock and leaves a small root stub containing the child VCN. That root\\nstub can be larger than the existing resident value. For example, an\\nempty root with value_length 48 has an index area of 32 bytes, while the\\nlarge-index root stub needs index_length and allocated_size of 40 bytes.\\n\\nThe current code publishes the larger index.index_length and\\nindex.allocated_size before resizing the resident value. If the resize\\nreturns -ENOSPC, the recovery path can call ntfs_inode_add_attrlist(),\\nwhich looks attributes up again while the root header says\\nallocated_size 40 but the resident value still only provides 32 bytes of\\nindex area. Lookup-time $INDEX_ROOT validation then correctly rejects\\nthat transient layout as corrupt.\\n\\nThis reproduces as a generic/013 failure under qemu. In the failing run,\\nthe transient root had value_len=48, index_size=32, index_length=40, and\\nallocated_size=40, and ntfsprogs-plus ntfsck reported \\\"Corrupt index\\nroot in MFT record 1177\\\".\\n\\nWhen the root stub grows, resize the resident value before publishing the\\nlarger root header. If the resize fails, the old root remains valid for\\nrecovery lookups. Keep the existing header-before-resize ordering for\\nshrink or same-size cases so the resident value never temporarily\\nexposes an allocated_size beyond its bounds.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/ntfs/index.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"0a8ac0c1fa0b99a5b29002bc7f232ed7eafddef0\",\"lessThan\":\"38d444271604afc6381ddb5a181e391915c35fae\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"0a8ac0c1fa0b99a5b29002bc7f232ed7eafddef0\",\"lessThan\":\"0bb508fb3b97e4802ec727fd2af4d608f65dd190\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/ntfs/index.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"7.1\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"7.1\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.5\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0bb508fb3b97e4802ec727fd2af4d608f65dd190\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/38d444271604afc6381ddb5a181e391915c35fae\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-18T11:07:30+00:00",
      "cve": "CVE-2026-72211",
      "id": "CVE-2026-72211",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ntfs: grow index root value before reparent header update",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72211.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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