CVE-2026-68145 (GCVE-0-2026-68145)

Vulnerability from cvelistv5 – Published: 2026-08-10 11:59 – Updated: 2026-08-23 12:45
VLAI
Title
iomap: fix out-of-bounds bitmap_set() with zero-length range
Summary
In the Linux kernel, the following vulnerability has been resolved: iomap: fix out-of-bounds bitmap_set() with zero-length range ifs_set_range_dirty() and ifs_set_range_uptodate() compute last_blk as (off + len - 1) >> i_blkbits. When off is 0 and len is 0, the unsigned subtraction underflows to SIZE_MAX, producing a huge last_blk and nr_blks value that causes bitmap_set() to write far beyond the ifs->state allocation. Regarding ifs_set_range_uptodate(), it is temporarily safe because len cannot be passed in as 0. However, for ifs_set_range_dirty() this is reachable from __iomap_write_end(): when copy_folio_from_iter_atomic() returns 0 (e.g. user buffer fault) and the folio is already uptodate, the guard at the top of __iomap_write_end() does not trigger because !folio_test_uptodate() is false, and iomap_set_range_dirty() is called with copied == 0. Add a !len guard to both functions before the computation, so that a zero-length range is a no-op.
Severity
7.8 (High)
CVSS:3.1/AV:L/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: 4ce02c67972211be488408c275c8fbf19faf29b3 , < 48829622212f6b8f49155889aecc818ba28ba680 (git)
Affected: 4ce02c67972211be488408c275c8fbf19faf29b3 , < fb4fad9105c88b1d82f1b3c39e3b6abea8249af6 (git)
Affected: 4ce02c67972211be488408c275c8fbf19faf29b3 , < 7037e7bdcd26f46c080b8ce307dee5cb471c4b7c (git)
Affected: 4ce02c67972211be488408c275c8fbf19faf29b3 , < c5b6a48a8a716a7730e39af1cad083dc4ec955ce (git)
Affected: 4ce02c67972211be488408c275c8fbf19faf29b3 , < 9c7d8f7c8994c790fca501dc45ce66e7356cbe05 (git)
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Linux Linux Affected: 6.6
Unaffected: 0 , < 6.6 (semver)
Unaffected: 6.6.153 , ≤ 6.6.* (semver)
Unaffected: 6.12.101 , ≤ 6.12.* (semver)
Unaffected: 6.18.42 , ≤ 6.18.* (semver)
Unaffected: 7.1.6 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niomap: fix out-of-bounds bitmap_set() with zero-length range\n\nifs_set_range_dirty() and ifs_set_range_uptodate() compute last_blk\nas (off + len - 1) \u003e\u003e i_blkbits.  When off is 0 and len is 0, the\nunsigned subtraction underflows to SIZE_MAX, producing a huge\nlast_blk and nr_blks value that causes bitmap_set() to write far\nbeyond the ifs-\u003estate allocation.\n\nRegarding ifs_set_range_uptodate(), it is temporarily safe because len\ncannot be passed in as 0. However, for ifs_set_range_dirty() this is\nreachable from __iomap_write_end(): when copy_folio_from_iter_atomic()\nreturns 0 (e.g. user buffer fault) and the folio is already uptodate,\nthe guard at the top of __iomap_write_end() does not trigger because\n!folio_test_uptodate() is false, and iomap_set_range_dirty() is called\nwith copied == 0.\n\nAdd a !len guard to both functions before the computation, so that a\nzero-length range is a no-op."
        }
      ],
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
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              "value": "AV:L - The bug is reached via the buffered write() path through iomap_file_buffered_write() when copy_folio_from_iter_atomic() returns 0; NFS/ksmbd server writes use kernel bvec iterators and do not hit this user-buffer fault path.\nAC:L - An attacker can reliably trigger copied==0 by racing munmap/remap against write() on an already-uptodate folio (TOCTOU after fault_in_iov_iter_readable), controlling both sides of the race on systems where folio size exceeds filesystem block size.\nPR:L - Only standard local write permission to a file on an iomap-backed filesystem (XFS, GFS2, FUSE writeback-cache, zonefs, NTFS) is required; no CAP_SYS_ADMIN or other elevated capability is needed beyond creating/triggering writes to attacker-writable files.\nUI:N - Exploitation requires only the attacker\u0027s own write operations to a writable file; no action by another user or administrator (such as mounting a filesystem or opening a file on the victim\u0027s behalf) is needed.\nS:U - Successful exploitation corrupts host kernel heap memory and enables local privilege escalation within the same kernel security domain; it does not inherently cross VM, container, or IOMMU boundaries.\nC:H - ifs_set_range_dirty() with len==0 underflows to SIZE_MAX and bitmap_set() writes far beyond the small kzalloc_flex(ifs-\u003estate) allocation, corrupting adjacent kmalloc objects in ways that can be leveraged for arbitrary kernel memory disclosure.\nI:H - The out-of-bounds bitmap_set() is a large heap overwrite primitive adjacent to the iomap_folio_state allocation, enabling control of kernel data structures and arbitrary code execution via standard heap exploitation techniques.\nA:H - The massive out-of-bounds write can immediately corrupt critical kernel heap metadata or adjacent objects, causing kernel oops/panic or unrecoverable memory corruption even before full exploitation is attempted."
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    "cveId": "CVE-2026-68145",
    "datePublished": "2026-08-10T11:59:09.721Z",
    "dateReserved": "2026-07-30T09:28:09.371Z",
    "dateUpdated": "2026-08-23T12:45:56.875Z",
    "state": "PUBLISHED"
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      "percentile": "0.02703"
    },
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      "id": "msrc_CVE-2026-68145",
      "initial_release_date": "2026-08-11T01:09:48.000Z",
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      "source": "Microsoft CSAF VEX",
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      "version": "4"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niomap: fix out-of-bounds bitmap_set() with zero-length range\n\nifs_set_range_dirty() and ifs_set_range_uptodate() compute last_blk\nas (off + len - 1) \u003e\u003e i_blkbits.  When off is 0 and len is 0, the\nunsigned subtraction underflows to SIZE_MAX, producing a huge\nlast_blk and nr_blks value that causes bitmap_set() to write far\nbeyond the ifs-\u003estate allocation.\n\nRegarding ifs_set_range_uptodate(), it is temporarily safe because len\ncannot be passed in as 0. However, for ifs_set_range_dirty() this is\nreachable from __iomap_write_end(): when copy_folio_from_iter_atomic()\nreturns 0 (e.g. user buffer fault) and the folio is already uptodate,\nthe guard at the top of __iomap_write_end() does not trigger because\n!folio_test_uptodate() is false, and iomap_set_range_dirty() is called\nwith copied == 0.\n\nAdd a !len guard to both functions before the computation, so that a\nzero-length range is a no-op."
          }
        ],
        "id": "CVE-2026-68145",
        "lastModified": "2026-08-23T13:16:33.943",
        "metrics": {
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                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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      "current_release_date": "2026-09-04T07:52:35+00:00",
      "cve": "CVE-2026-68145",
      "id": "CVE-2026-68145",
      "initial_release_date": "2026-08-10T00:00:00+00:00",
      "product_status:fixed": "612",
      "product_status:known_not_affected": "112",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: iomap: fix out-of-bounds bitmap_set() with zero-length range",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-68145.json",
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    }
  }
}



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