GHSA-6F82-HFHW-X2GC

Vulnerability from github – Published: 2026-07-25 12:31 – Updated: 2026-07-27 06:30
VLAI
Details

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

exfat: bound uniname advance in exfat_find_dir_entry()

In exfat_find_dir_entry(), each TYPE_EXTEND (file name) entry advances the output pointer by a fixed amount while the loop guard only tracks the accumulated name length:

if (++order == 2)
    uniname = p_uniname->name;
else
    uniname += EXFAT_FILE_NAME_LEN;
len = exfat_extract_uni_name(ep, entry_uniname);
name_len += len;
unichar = *(uniname+len);
*(uniname+len) = 0x0;

uniname grows by EXFAT_FILE_NAME_LEN (15) per name entry, but name_len grows only by the actual extracted length, which is shorter when a name fragment contains an early NUL. The only guard is name_len >= MAX_NAME_LENGTH, so a crafted directory with many short name fragments lets uniname run far past the p_uniname->name[MAX_NAME_LENGTH + 3] buffer while name_len stays small, causing an out-of-bounds read and write at *(uniname+len).

The sibling extractor exfat_get_uniname_from_ext_entry() already stops on a short fragment (the lockstep len != EXFAT_FILE_NAME_LEN guard added in commit d42334578eba ("exfat: check if filename entries exceeds max filename length")); exfat_find_dir_entry() never got the equivalent. Track the per-entry write offset as a count and reject a fragment once the offset, or the offset plus the extracted length, would exceed MAX_NAME_LENGTH, before forming the output pointer.

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-64296"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-25T10:17:10Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nexfat: bound uniname advance in exfat_find_dir_entry()\n\nIn exfat_find_dir_entry(), each TYPE_EXTEND (file name) entry advances the\noutput pointer by a fixed amount while the loop guard only tracks the\naccumulated name length:\n\n\tif (++order == 2)\n\t\tuniname = p_uniname-\u003ename;\n\telse\n\t\tuniname += EXFAT_FILE_NAME_LEN;\n\tlen = exfat_extract_uni_name(ep, entry_uniname);\n\tname_len += len;\n\tunichar = *(uniname+len);\n\t*(uniname+len) = 0x0;\n\nuniname grows by EXFAT_FILE_NAME_LEN (15) per name entry, but name_len\ngrows only by the actual extracted length, which is shorter when a name\nfragment contains an early NUL.  The only guard is\n`name_len \u003e= MAX_NAME_LENGTH`, so a crafted directory with many short\nname fragments lets uniname run far past the\np_uniname-\u003ename[MAX_NAME_LENGTH + 3] buffer while name_len stays small,\ncausing an out-of-bounds read and write at *(uniname+len).\n\nThe sibling extractor exfat_get_uniname_from_ext_entry() already stops\non a short fragment (the lockstep `len != EXFAT_FILE_NAME_LEN` guard\nadded in commit d42334578eba (\"exfat: check if filename entries exceeds\nmax filename length\")); exfat_find_dir_entry() never got the\nequivalent.  Track the per-entry write offset as a count and reject a\nfragment once the offset, or the offset plus the extracted length, would\nexceed MAX_NAME_LENGTH, before forming the output pointer.",
  "id": "GHSA-6f82-hfhw-x2gc",
  "modified": "2026-07-27T06:30:31Z",
  "published": "2026-07-25T12:31:30Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64296"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/33c0b96d7e1672be1de0053786637ea46fb81507"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3a1230e7b043c62737b05a3e9275ca83a43ad20a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/727bf7783a2936ffd55c628dddfd69343e511dcf"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/72a2589d82eb001c94b74bcfe6f9a599bd9bef60"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c8e041c68c0bbb73aa62371ee63947bb6949d8b2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ce4736c1e6c4cfbf1ac409a8c328a0b69546c9a0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cf85180b8a015029ee147694eaf4e0b3537e9432"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fae76a94b35ee8c0e2eb6f64caca01d75c6d34e4"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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