CVE-2026-72367 (GCVE-0-2026-72367)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:56 – Updated: 2026-08-17 05:43
VLAI
Title
iomap: guard io_size EOF trim against concurrent truncate underflow
Summary
In the Linux kernel, the following vulnerability has been resolved: iomap: guard io_size EOF trim against concurrent truncate underflow iomap: fix zero padding data issue in concurrent append writes changed ioend accounting so that io_size tracks only valid data within EOF. This trims io_size when a writeback range extends past end_pos: ioend->io_size += map_len; if (ioend->io_offset + ioend->io_size > end_pos) ioend->io_size = end_pos - ioend->io_offset; However, if end_pos ends up below ioend->io_offset, the subtraction becomes negative and is stored in size_t io_size, causing an unsigned wrap to a huge value. This can happen when writeback continues past byte-level EOF up to a block-aligned range, or when a concurrent truncate shrinks the file after end_pos was sampled in iomap_writeback_handle_eof(). A wrapped io_size can mislead append detection and corrupt completion-time size handling, since filesystem end_io paths consume io_size for decisions such as on-disk EOF updates and unwritten/COW completion ranges. Fix this by clamping io_size to zero when EOF has moved to or before the ioend start offset. This preserves the original intent of trimming io_size to valid in-EOF data while avoiding the underflow.
Severity
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 51d20d1dacbec589d459e11fc88fbca419f84a99 , < 1f38f65bf965fce9aa159d45c5347538f56c5973 (git)
Affected: 51d20d1dacbec589d459e11fc88fbca419f84a99 , < 7f7780abb4c0fdc9a2603aea8e985ff14ee900e0 (git)
Affected: 51d20d1dacbec589d459e11fc88fbca419f84a99 , < 55ec50d046c03b3724741957f7b007856e36dbe7 (git)
Affected: 82c59a86a247a8970d353d10f52a37e5564fb137 (git)
Affected: 6.12.10 , < 6.13 (semver)
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Linux Linux Affected: 6.13
Unaffected: 0 , < 6.13 (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niomap: guard io_size EOF trim against concurrent truncate underflow\n\niomap: fix zero padding data issue in concurrent append writes\nchanged ioend accounting so that io_size tracks only valid data\nwithin EOF.  This trims io_size when a writeback range extends\npast end_pos:\n\n    ioend-\u003eio_size += map_len;\n    if (ioend-\u003eio_offset + ioend-\u003eio_size \u003e end_pos)\n        ioend-\u003eio_size = end_pos - ioend-\u003eio_offset;\n\nHowever, if end_pos ends up below ioend-\u003eio_offset, the subtraction\nbecomes negative and is stored in size_t io_size, causing an unsigned\nwrap to a huge value.  This can happen when writeback continues past\nbyte-level EOF up to a block-aligned range, or when a concurrent\ntruncate shrinks the file after end_pos was sampled in\niomap_writeback_handle_eof().\n\nA wrapped io_size can mislead append detection and corrupt\ncompletion-time size handling, since filesystem end_io paths consume\nio_size for decisions such as on-disk EOF updates and unwritten/COW\ncompletion ranges.\n\nFix this by clamping io_size to zero when EOF has moved to or before\nthe ioend start offset.  This preserves the original intent of trimming\nio_size to valid in-EOF data while avoiding the underflow."
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            "baseSeverity": "HIGH",
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            "version": "3.1"
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              "value": "AV:N - On XFS/GFS2/NTFS backends exposed via nfsd or ksmbd, a remote client can trigger iomap buffered writeback by issuing concurrent WRITE and truncate/SETATTR operations over the network without local shell access.\nAC:L - The attacker controls both sides of the race by concurrently writing dirty pages and truncating the same file (local threads or parallel NFS/SMB requests); no uncontrollable memory layout or rare kernel configuration is required.\nPR:L - Exploitation requires write and truncate permission on the target file (authenticated NFS/SMB client or local unprivileged user with file write access); this is not a pre-authentication network code path.\nUI:N - No victim interaction is needed beyond the attacker\u0027s own write and truncate I/O; writeback is driven automatically by the VFS/page-cache path once pages are dirtied.\nS:U - Impact is confined to kernel/filesystem integrity within the same security authority (metadata corruption, incorrect extent completion, possible local privilege escalation), not a VM escape or cross-authority boundary.\nC:H - A wrapped io_size propagates into XFS completion paths (COW convert/end, unwritten conversion, append detection), potentially remapping or exposing unintended on-disk extents and data beyond the legitimate EOF-trimmed range.\nI:H - Huge bogus io_size drives xfs_reflink_convert_cow, xfs_reflink_end_cow, xfs_iomap_write_unwritten, and xfs_setfilesize with corrupted ranges, enabling incorrect on-disk metadata updates and file content modification.\nA:H - Corrupted ioend accounting can trigger pathological XFS extent walks, ASSERT failures, filesystem shutdown, or hung writeback during I/O completion, causing kernel oops or sustained denial of service."
            }
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        {
          "url": "https://git.kernel.org/stable/c/55ec50d046c03b3724741957f7b007856e36dbe7"
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    "cveId": "CVE-2026-72367",
    "datePublished": "2026-08-15T05:56:04.669Z",
    "dateReserved": "2026-08-09T03:40:39.922Z",
    "dateUpdated": "2026-08-17T05:43:20.980Z",
    "state": "PUBLISHED"
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            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niomap: guard io_size EOF trim against concurrent truncate underflow\n\niomap: fix zero padding data issue in concurrent append writes\nchanged ioend accounting so that io_size tracks only valid data\nwithin EOF.  This trims io_size when a writeback range extends\npast end_pos:\n\n    ioend-\u003eio_size += map_len;\n    if (ioend-\u003eio_offset + ioend-\u003eio_size \u003e end_pos)\n        ioend-\u003eio_size = end_pos - ioend-\u003eio_offset;\n\nHowever, if end_pos ends up below ioend-\u003eio_offset, the subtraction\nbecomes negative and is stored in size_t io_size, causing an unsigned\nwrap to a huge value.  This can happen when writeback continues past\nbyte-level EOF up to a block-aligned range, or when a concurrent\ntruncate shrinks the file after end_pos was sampled in\niomap_writeback_handle_eof().\n\nA wrapped io_size can mislead append detection and corrupt\ncompletion-time size handling, since filesystem end_io paths consume\nio_size for decisions such as on-disk EOF updates and unwritten/COW\ncompletion ranges.\n\nFix this by clamping io_size to zero when EOF has moved to or before\nthe ioend start offset.  This preserves the original intent of trimming\nio_size to valid in-EOF data while avoiding the underflow."
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        "lastModified": "2026-08-17T06:18:40.890",
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                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
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                "scope": "UNCHANGED",
                "userInteraction": "NONE",
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        "vulnStatus": "Received"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-19T17:41:23+00:00",
      "cve": "CVE-2026-72367",
      "id": "CVE-2026-72367",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: iomap: guard io_size EOF trim against concurrent truncate underflow",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72367.json",
      "version": "3"
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      "current_release_date": "2026-09-15T01:26:28Z",
      "cve": "CVE-2026-72367",
      "id": "CVE-2026-72367",
      "initial_release_date": "2026-09-01T17:14:05Z",
      "product_status:known_affected": "41",
      "product_status:known_not_affected": "321",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-72367",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-72367.json",
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    }
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}



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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.
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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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