Bug 2507401 (CVE-2026-64533)

Summary: CVE-2026-64533 kernel: fs/ntfs3: validate lcns_follow in log_replay conversion
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's ntfs3 filesystem driver. A local attacker could exploit this vulnerability by crafting a specially designed NTFS filesystem image. This flaw allows an attacker to cause an out-of-bounds memory write during the log replay conversion process, potentially leading to memory corruption and system instability or denial of service.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-07-27 08:01:29 UTC 
In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: validate lcns_follow in log_replay conversion

log_replay() converts DIR_PAGE_ENTRY_32 records into DIR_PAGE_ENTRY
records when replaying version 0 restart tables.

During this conversion, the memmove() length is derived directly from
the on-disk lcns_follow field:

	memmove(&dp->vcn, &dp0->vcn_low,
		2 * sizeof(u64) +
				le32_to_cpu(dp->lcns_follow) * sizeof(u64));

check_rstbl() validates restart table structure, but does not constrain
per-entry lcns_follow values relative to the entry size. A malformed
filesystem image can provide an oversized lcns_follow value, causing
the conversion memmove() to access memory beyond the bounds of the
allocated restart table buffer.

The same field is later used to bound iteration over page_lcns[],
so validating lcns_follow during conversion also prevents downstream
out-of-bounds access from the same malformed metadata.

Compute the maximum valid lcns_follow from the already-validated
restart table entry size and reject entries that exceed this bound.
Reuse the existing t16/t32 scratch variables already declared in
log_replay() to avoid introducing new declarations.

[almaz.alexandrovich: fixed the conflicts]
Comment 1 TEJ RATHI 2026-07-29 06:16:21 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026072734-CVE-2026-64533-8c8b@gregkh/T