Bug 2516550 (CVE-2026-72471)

Summary: CVE-2026-72471 kernel: fs/ntfs3: prevent potential lcn remains uninitialized
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the NTFS3 filesystem driver in the Linux kernel. An uninitialized value vulnerability exists when processing NTFS3 filesystem operations. This can lead to a kernel crash, resulting in a denial of service (DoS) for the affected system. A local attacker could potentially exploit this by interacting with a specially crafted NTFS3 filesystem.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-08-15 06:18:25 UTC 
In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: prevent potential lcn remains uninitialized

The target VCN being sought was not found within runs[0], causing
run_lookup() to return false. This causes run_lookup_entry() to return
false, which in turn results in a len value of 0, and the new parameter
passed to attr_data_get_block() is NULL. Collectively, these factors
ultimately cause attr_data_get_block_locked() to exit prematurely without
initializing lcn, thereby triggering [1].

To prevent [1], the clen check within ni_seek_data_or_hole() has been
moved to occur before the lcn check.

[1]
BUG: KMSAN: uninit-value in ni_seek_data_or_hole+0x24f/0x5f0 fs/ntfs3/frecord.c:2862
 ni_seek_data_or_hole+0x24f/0x5f0 fs/ntfs3/frecord.c:2862
 ntfs_llseek+0x22a/0x4a0 fs/ntfs3/file.c:1530
 vfs_llseek fs/read_write.c:391 [inline]
Comment 1 gkamathe 2026-08-18 15:27:27 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081535-CVE-2026-72471-5abe@gregkh/T