Bug 2516467 (CVE-2026-72195)

Summary: CVE-2026-72195 kernel: fs/ntfs3: bound attr_off in UpdateResidentValue against data_off
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's ntfs3 file system driver. An integer underflow vulnerability occurs in the UpdateResidentValue function when processing a maliciously crafted Log Record Header (LRH). This underflow can lead to an incorrect calculation of data_size, allowing subsequent operations to read up to 4 Gigabytes (GiB) of memory beyond the intended buffer. This out-of-bounds read could result in information disclosure.
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Description OSIDB Bzimport 2026-08-15 06:14:05 UTC 
In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: bound attr_off in UpdateResidentValue against data_off

In do_action()'s UpdateResidentValue case (fslog.c:3307),
lrh->attr_off and lrh->redo_len come from the on-disk LRH.
When they satisfy aoff + dlen < attr->res.data_off, the
assignment

	attr->res.data_size = cpu_to_le32(aoff + dlen - data_off);

underflows to ~4 GiB (e.g. 0xFFFFFFF9 when aoff=0x10, dlen=1,
data_off=0x18).  Subsequent code that reads attr->res.data_size
to walk the resident attribute payload would then read up to
4 GiB past the 1024-byte MFT record allocation.

The existing mi_enum_attr() defense in fs/ntfs3/record.c:287
catches the corrupted data_size on the next attribute walk
and fails the mount, but only on the path that walks all
attributes.  A read site that picks an attribute by name and
reads its data_size without re-validating is not covered.
Validate aoff against data_off and asize at the source.

Reproduced under UML+KASAN on mainline 8d90b09e6741 via
pr_warn-only probe: with aoff=0x10 and data_off=0x18, the
post-assignment data_size is 0xfffffff9 (mount then fails
at -22 from mi_enum_attr).

[almaz.alexandrovich: clang-formatted the changes]
Comment 1 Keith Grant 2026-08-18 14:59:36 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081542-CVE-2026-72195-1892@gregkh/T