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CVE-2026-72186 (GCVE-0-2026-72186)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:53 – Updated: 2026-08-17 05:41
VLAI
Title
ntfs: make system files immutable to prevent corruption
Summary
In the Linux kernel, the following vulnerability has been resolved: ntfs: make system files immutable to prevent corruption When a system file such as $Bitmap is exposed via show_sys_files and written from userspace, the volume is corrupted and, because the cluster allocator scans $Bitmap through the same inode's page cache, a write to $Bitmap also deadlocks writeback against the folio it already holds locked. These files are maintained by the driver itself and have no valid reason to be written through the file interface. Mark base metadata files (mft_no < FILE_first_user) as immutable during inode read so the VFS rejects write, mmap, truncate and unlink with -EPERM. Directories are skipped so the root and $Extend remain usable. Internal metadata updates do not go through the VFS write path and are unaffected.
Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: af0db57d4293cc9fe6ce99fb5592dc2652228c9d , < 8f313e92522ac41d273ea137db13ea8a8df2beed (git)
Affected: af0db57d4293cc9fe6ce99fb5592dc2652228c9d , < f72df3a4c33b64de3418ec74d1ad4f028e09d161 (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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          "programFiles": [
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        }
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              "value": "AV:N - fs/ntfs registers ntfs_export_ops; remote nfsd/ksmbd write RPCs reach ntfs_file_write_iter on $Bitmap, and dual-boot/shared NTFS volumes are commonly rw-mounted and network-exported on NAS/hybrid servers.\nAC:L - Without S_IMMUTABLE, opening $Bitmap by name and writing is deterministic; expanding $Bitmap triggers ntfs_attr_map_cluster while lcnalloc holds the same folio locked, deadlocking writeback as documented in the fix commit.\nPR:N - Exploitation needs only permission to write on a mounted NTFS volume (default i_mode 0777 with fmask=0, uid/gid mount options, authenticated SMB/NFS client, or guest write); no CAP_SYS_ADMIN or init-namespace root is required at trigger time.\nUI:N - Once an administrator has rw-mounted and optionally exported the NTFS volume, the attacker issues normal write/mmap/truncate/unlink to $Bitmap or other mft_no\u003cFILE_first_user files; no per-attack victim interaction is required.\nS:U - Impact is on-disk NTFS metadata corruption and kernel thread deadlock within the host filesystem/kernel authority; this is standard filesystem abuse, not a VM escape, container breakout, or IOMMU boundary bypass.\nC:N - The flaw is attacker-initiated writes to exposed system files and resulting metadata corruption; it does not perform kernel out-of-bounds reads, use-after-free, or other memory-disclosure primitives.\nI:H - Writing $Bitmap (or $MFT, $LogFile, $Boot, etc.) lets an attacker directly control cluster-allocation state, causing arbitrary on-disk metadata corruption and steered overwrites of live file data clusters across the volume.\nA:H - Concurrent $Bitmap writes deadlock the cluster allocator against writeback on the same folio, hanging kernel I/O threads, and corrupted allocation bitmaps can render the NTFS volume inconsistent and unusable on remount."
            }
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          "url": "https://git.kernel.org/stable/c/8f313e92522ac41d273ea137db13ea8a8df2beed"
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          "url": "https://git.kernel.org/stable/c/f72df3a4c33b64de3418ec74d1ad4f028e09d161"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72186",
    "datePublished": "2026-08-15T05:53:48.127Z",
    "dateReserved": "2026-08-09T03:40:39.911Z",
    "dateUpdated": "2026-08-17T05:41:16.318Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-18T15:15:52+00:00",
      "cve": "CVE-2026-72186",
      "id": "CVE-2026-72186",
      "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: make system files immutable to prevent corruption",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72186.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.

Sightings

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Nomenclature

  • 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.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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