GHSA-7XR2-RX94-5F89

Vulnerability from github – Published: 2026-09-16 09:30 – Updated: 2026-09-16 15:30
VLAI
Details

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

ext4: fix out-of-bounds read in ext4_read_inline_dir()

ext4_read_inline_dir() can read a dirent header past the end of its inline buffer, triggering a slab-out-of-bounds read during getdents64():

BUG: KASAN: slab-out-of-bounds in __ext4_check_dir_entry Read of size 2 at addr ffff88800f3dd23c by task exploit/148 ... __ext4_check_dir_entry ext4_read_inline_dir iterate_dir

The dirent payload lives in a buffer of exactly inline_size bytes:

dir_buf = kmalloc(inline_size, GFP_NOFS);

but iteration runs in a position space extra_offset bytes larger (extra_size = extra_offset + inline_size) so the synthetic "." and ".." land at their block-dir offsets. A dirent is formed at "dir_buf + pos - extra_offset", yet the ext4_check_dir_entry() length argument uses the larger extra_size. A position whose dirent header would extend past extra_size is therefore accepted, and the rescan loop's rec_len probe and ext4_check_dir_entry() dereference de->rec_len before the entry is rejected.

Reject a position whose minimum-size dirent header would not fit within extra_size before forming de, in both the rescan and main loops, and pass inline_size rather than extra_size to ext4_check_dir_entry() so the length check matches the physical buffer.

Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-89786"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-16T09:17:09Z",
    "severity": "CRITICAL"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix out-of-bounds read in ext4_read_inline_dir()\n\next4_read_inline_dir() can read a dirent header past the end of its inline\nbuffer, triggering a slab-out-of-bounds read during getdents64():\n\n  BUG: KASAN: slab-out-of-bounds in __ext4_check_dir_entry\n  Read of size 2 at addr ffff88800f3dd23c by task exploit/148\n   ...\n   __ext4_check_dir_entry\n   ext4_read_inline_dir\n   iterate_dir\n\nThe dirent payload lives in a buffer of exactly inline_size bytes:\n\n\tdir_buf = kmalloc(inline_size, GFP_NOFS);\n\nbut iteration runs in a position space extra_offset bytes larger\n(extra_size = extra_offset + inline_size) so the synthetic \".\" and \"..\"\nland at their block-dir offsets. A dirent is formed at \"dir_buf + pos -\nextra_offset\", yet the ext4_check_dir_entry() length argument uses the\nlarger extra_size. A position whose dirent header would extend past\nextra_size is therefore accepted, and the rescan loop\u0027s rec_len probe and\next4_check_dir_entry() dereference de-\u003erec_len before the entry is rejected.\n\nReject a position whose minimum-size dirent header would not fit within\nextra_size before forming de, in both the rescan and main loops, and pass\ninline_size rather than extra_size to ext4_check_dir_entry() so the length\ncheck matches the physical buffer.",
  "id": "GHSA-7xr2-rx94-5f89",
  "modified": "2026-09-16T15:30:57Z",
  "published": "2026-09-16T09:30:30Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89786"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1a1dea633b724a1c042dbcdb1fed27f410916688"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/36bf17bb90cdf7a623499b624b05acde4d2feef5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5fd20d4e50dd6e460b3ea8e4396f8553d4526f8f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6702c7da86d8cdb88d0fc57166286e115ffeb8c0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9333cc809f0a89e001b814155a6cb8903a6274df"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b060861f662d4826dc700a1c3584243bb3474cfe"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d1e7c186555ad65554fd2f2b02f5a539aa35ae48"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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