CVE-2026-64532 in Linux
Summary
by MITRE • 07/27/2026
In the Linux kernel, the following vulnerability has been resolved:
fs/ntfs3: bound NTFS_DE view.data_off in UpdateRecordData{Root,Allocation}
In do_action()'s UpdateRecordDataRoot (fslog.c:3489) and UpdateRecordDataAllocation (fslog.c:3697) cases, the memmove destination is `Add2Ptr(e, le16_to_cpu(e->view.data_off))`, where e->view.data_off comes from an on-disk NTFS_DE inside an INDEX_ROOT or INDEX_BUFFER. Neither case validates view.data_off + dlen against e->size; the existing check_if_index_root / check_if_alloc_index helpers walk the entry chain and validate the entry's offset, but not its internal view fields.
The neighbouring read sites (e.g., fs/ntfs3/index.c when iterating view entries) check view.data_off + view.data_size <= e->size. Apply the same bound at the two memmove sites.
Reproduced under UML+KASAN on mainline 8d90b09e6741 via pr_warn-only probe instrumentation: with view.data_off forced to 0xFFFC, the memmove writes 32 bytes past the end of the NTFS_DE.
This is similar in shape to Pavitra Jha's 2026-05-02 patch "fs/ntfs3: prevent oob in case UpdateRecordDataRoot" (<[email protected]>) which proposes calling ntfs3_bad_de_range(); that helper does not exist in mainline. This patch uses inline checks.
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Analysis
by VulDB Data Team • 07/27/2026
The vulnerability resides within the linux kernel's ntfs3 filesystem implementation where improper bounds checking leads to potential out-of-bounds memory access during record data updates. Specifically, the issue manifests in two functions UpdateRecordDataRoot and UpdateRecordDataAllocation located in fslog.c at lines 3489 and 3697 respectively. These functions handle operations on ntfs directory entries that contain index root and allocation structures, where each entry includes a view.data_off field that references data within the entry structure itself.
The core technical flaw occurs when the memmove operation attempts to copy data starting from Add2Ptr(e, le16_to_cpu(e->view.data_off)) without validating whether this calculated address plus the data length exceeds the bounds of the containing entry structure. While the existing validation functions check_if_index_root and check_if_alloc_index properly validate offsets within the entry chain, they fail to validate internal view fields including data_off and data_size. This discrepancy creates a scenario where maliciously crafted ntfs filesystem structures could trigger memory corruption.
The operational impact of this vulnerability extends beyond simple memory corruption as it represents a classic buffer overflow condition that could potentially lead to privilege escalation or system instability. The issue is particularly concerning because the affected code paths are invoked during normal filesystem operations, making exploitation feasible through crafted ntfs images or file systems with malformed metadata structures. Memory access patterns indicate that an attacker could force data_off to a value such as 0xFFFC which would cause a 32-byte write past the end of the ntfs_de structure.
This vulnerability aligns with CWE-129 and CWE-787 categories, representing improper input validation and out-of-bounds read/write conditions respectively. From an attack perspective, it maps to ATT&CK technique T1059.003 for execution through filesystem manipulation and potentially T1068 for privilege escalation. The fix implements bounds checking similar to existing patterns used elsewhere in the codebase within fs/ntfs3/index.c where view.data_off + view.data_size <= e->size validation already exists. This approach ensures consistency with established security practices and prevents the type of out-of-bounds memory operations that could be exploited by attackers.
The patch resolves this by applying identical bounds checking at the two memmove sites, preventing potential buffer overflows that could occur when data_off values are maliciously crafted to point beyond the valid entry boundaries. This remediation addresses the root cause by ensuring all memory operations respect the structural limits of ntfs directory entries, thereby maintaining kernel stability and preventing potential exploitation scenarios that could compromise system integrity. The solution maintains compatibility with existing filesystem operations while strengthening security boundaries through explicit validation of internal view fields.