GHSA-H945-5WHJ-H8MC
Vulnerability from github – Published: 2026-09-17 18:31 – Updated: 2026-09-17 18:31In the Linux kernel, the following vulnerability has been resolved:
fs/ntfs3: fix integer overflow in MFT cluster validation
In ntfs_init_from_boot(), the boot sector's MFT cluster numbers are validated against the volume size with:
if (mlcn * sct_per_clst >= sectors ||
mlcn2 * sct_per_clst >= sectors)
goto out;
mlcn and mlcn2 are u64 fields read directly from the boot sector. sct_per_clst is bounded above by 4096 (true_sectors_per_clst() plus the is_power_of_2() check below it), but the multiplication is done in u64 and wraps when mlcn (or mlcn2) is large enough -- e.g. mlcn near 2^62 with sct_per_clst == 4 wraps to 0, which compares below any non-zero 'sectors', so the check is bypassed and the malformed record is accepted.
The accepted mlcn is then used unchanged in
sbi->mft.lbo = mlcn << cluster_bits;
In practice the resulting reads fail at the block layer (sb_bread() returns NULL via grow_buffers()'s check_mul_overflow() guard), so today this manifests as mount failing in odd places rather than as something more dangerous, but the validation step is still wrong and there is no reason for callers to rely on the block layer to catch a value that should never have been accepted in the first place.
Use check_mul_overflow() to compute the two sector positions and fail the mount if either multiplication wraps; this preserves the existing semantics (mlcn * sct_per_clst >= sectors) instead of switching to division (mlcn >= sectors / sct_per_clst), which would tighten the check at edge cases where 'sectors' is not a multiple of sct_per_clst. The check_*_overflow() style is the one ntfs3 already uses for similar on-disk arithmetic in fs/ntfs3/run.c.
{
"affected": [],
"aliases": [
"CVE-2026-90200"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:17:14Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/ntfs3: fix integer overflow in MFT cluster validation\n\nIn ntfs_init_from_boot(), the boot sector\u0027s MFT cluster numbers are\nvalidated against the volume size with:\n\n\tif (mlcn * sct_per_clst \u003e= sectors ||\n\t mlcn2 * sct_per_clst \u003e= sectors)\n\t\tgoto out;\n\nmlcn and mlcn2 are u64 fields read directly from the boot sector.\nsct_per_clst is bounded above by 4096 (true_sectors_per_clst() plus\nthe is_power_of_2() check below it), but the multiplication is done\nin u64 and wraps when mlcn (or mlcn2) is large enough -- e.g. mlcn\nnear 2^62 with sct_per_clst == 4 wraps to 0, which compares below\nany non-zero \u0027sectors\u0027, so the check is bypassed and the malformed\nrecord is accepted.\n\nThe accepted mlcn is then used unchanged in\n\n\tsbi-\u003emft.lbo = mlcn \u003c\u003c cluster_bits;\n\nIn practice the resulting reads fail at the block layer (sb_bread()\nreturns NULL via grow_buffers()\u0027s check_mul_overflow() guard), so\ntoday this manifests as mount failing in odd places rather than as\nsomething more dangerous, but the validation step is still wrong\nand there is no reason for callers to rely on the block layer to\ncatch a value that should never have been accepted in the first\nplace.\n\nUse check_mul_overflow() to compute the two sector positions and\nfail the mount if either multiplication wraps; this preserves the\nexisting semantics (mlcn * sct_per_clst \u003e= sectors) instead of\nswitching to division (mlcn \u003e= sectors / sct_per_clst), which\nwould tighten the check at edge cases where \u0027sectors\u0027 is not a\nmultiple of sct_per_clst. The check_*_overflow() style is the\none ntfs3 already uses for similar on-disk arithmetic in\nfs/ntfs3/run.c.",
"id": "GHSA-h945-5whj-h8mc",
"modified": "2026-09-17T18:31:55Z",
"published": "2026-09-17T18:31:55Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90200"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/169383d8914b8fe03464a83540b5b6de3e7831af"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/805cc5554b13d045dce9b03c13eaf015418739fd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c510c63873103a5da6a498fe537bdb5d6f8d03a2"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dc6d85de7e2656e56e10ff5ba514f2583a4f612b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f77a8d9fdf58e298b36564a44c27fadc617bdd28"
}
],
"schema_version": "1.4.0",
"severity": []
}
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