Linux hwe edge: In the Linux kernel, the following vulnerability has been resolved: ntfs: avoid calling post_write_mst_fixup() for invalid index_block… (CVE-2026-64431)
In the Linux kernel, the following vulnerability has been resolved: ntfs: avoid calling post_write_mst_fixup() for invalid index_block ntfs_icx_ib_sync_write() calls post_write_mst_fixup() when ntfs_ib_write() returns an error, intending to restore the buffer after a failed write. However, ntfs_ib_write() returns an error immediately if pre_write_mst_fixup() validation fails. The caller, ntfs_icx_ib_sync_write(), interprets any error as a write failure requiring rollback. It does not differentiate between I/O errors and validation failures, and calls post_write_mst_fixup() anyway. Since post_write_mst_fixup() assumes that the index_block contents is correct, it doesn't perform the boundary checks, which results in out-of-bounds memory access. An attacker can craft a malicious NTFS image with: - large index_block.usa_ofs offset, pointing outside the ntfs_record - index_block.usa_count = 0, causing integer underflow - or index_block.usa_count larger than actual number of sectors in the ntfs_record, causing out-of-bounds access KASAN reports describing the memory corruption: ================================================================== BUG: KASAN: slab-out-of-bounds in post_write_mst_fixup+0x19c/0x1d0 Read of size 2 at addr ffff8881586c9018 by task p/9428 Call Trace: <TASK> dump_stack_lvl+0x100/0x190 print_report+0x139/0x4ad ? post_write_mst_fixup+0x19c/0x1d0 ? __virt_addr_valid+0x262/0x500 ? post_write_mst_fixup+0x19c/0x1d0 kasan_report+0xe4/0x1d0 ? post_write_mst_fixup+0x19c/0x1d0 post_write_mst_fixup+0x19c/0x1d0 ntfs_icx_ib_sync_write+0x179/0x220 ntfs_inode_sync_filename+0x83d/0x1080 __ntfs_write_inode+0x1049/0x1480 ntfs_file_fsync+0x131/0x9b0 ================================================================== BUG: KASAN: slab-out-of-bounds in post_write_mst_fixup+0x1aa/0x1d0 Write of size 2 at addr ffff8881586c91fe by task p/9428 Call Trace: <TASK> dump_stack_lvl+0x100/0x190 print_report+0x139/0x4ad ? post_write_mst_fixup+0x1aa/0x1d0 ? __virt_addr_valid+0x262/0x500 ? post_write_mst_fixup+0x1aa/0x1d0 kasan_report+0xe4/0x1d0 ? post_write_mst_fixup+0x1aa/0x1d0 post_write_mst_fixup+0x1aa/0x1d0 ntfs_icx_ib_sync_write+0x179/0x220 ntfs_inode_sync_filename+0x83d/0x1080 __ntfs_write_inode+0x1049/0x1480 ntfs_file_fsync+0x131/0x9b0 ================================================================== Let's move the post_write_mst_fixup() call to ntfs_ib_write(). The ntfs_ib_write() function calls pre_write_mst_fixup() at the beginning. If the index_block contents is invalid, pre_write_mst_fixup() fails and ntfs_ib_write() returns early without calling post_write_mst_fixup() on bad index_block.
AI Analysis
Technical Summary
The Linux kernel NTFS driver had a vulnerability where ntfs_icx_ib_sync_write() called post_write_mst_fixup() after ntfs_ib_write() returned an error, without distinguishing between I/O errors and validation failures. Since post_write_mst_fixup() assumes valid index_block contents and does not perform boundary checks, this led to out-of-bounds memory access when the index_block was invalid. An attacker could craft a malicious NTFS image with large or malformed index_block.usa_ofs and usa_count values to trigger this memory corruption. The fix moves the post_write_mst_fixup() call into ntfs_ib_write(), preventing calls on invalid index_block data.
Potential Impact
The vulnerability causes out-of-bounds memory access in kernel space, which can lead to memory corruption. Although no specific exploit in the wild is known, this type of flaw could potentially be leveraged for denial of service or privilege escalation if exploited. The impact is limited to systems mounting or writing to malicious NTFS images.
Mitigation Recommendations
A fix has been implemented in the Linux kernel by relocating the post_write_mst_fixup() call to ntfs_ib_write(), ensuring it is only invoked after successful pre_write_mst_fixup() validation. Users should apply the updated Linux kernel version containing this fix. Patch status is not explicitly stated here; check the vendor or kernel mailing list advisories for the exact fixed kernel versions and apply updates accordingly.
Linux hwe edge: In the Linux kernel, the following vulnerability has been resolved: ntfs: avoid calling post_write_mst_fixup() for invalid index_block… (CVE-2026-64431)
Description
In the Linux kernel, the following vulnerability has been resolved: ntfs: avoid calling post_write_mst_fixup() for invalid index_block ntfs_icx_ib_sync_write() calls post_write_mst_fixup() when ntfs_ib_write() returns an error, intending to restore the buffer after a failed write. However, ntfs_ib_write() returns an error immediately if pre_write_mst_fixup() validation fails. The caller, ntfs_icx_ib_sync_write(), interprets any error as a write failure requiring rollback. It does not differentiate between I/O errors and validation failures, and calls post_write_mst_fixup() anyway. Since post_write_mst_fixup() assumes that the index_block contents is correct, it doesn't perform the boundary checks, which results in out-of-bounds memory access. An attacker can craft a malicious NTFS image with: - large index_block.usa_ofs offset, pointing outside the ntfs_record - index_block.usa_count = 0, causing integer underflow - or index_block.usa_count larger than actual number of sectors in the ntfs_record, causing out-of-bounds access KASAN reports describing the memory corruption: ================================================================== BUG: KASAN: slab-out-of-bounds in post_write_mst_fixup+0x19c/0x1d0 Read of size 2 at addr ffff8881586c9018 by task p/9428 Call Trace: <TASK> dump_stack_lvl+0x100/0x190 print_report+0x139/0x4ad ? post_write_mst_fixup+0x19c/0x1d0 ? __virt_addr_valid+0x262/0x500 ? post_write_mst_fixup+0x19c/0x1d0 kasan_report+0xe4/0x1d0 ? post_write_mst_fixup+0x19c/0x1d0 post_write_mst_fixup+0x19c/0x1d0 ntfs_icx_ib_sync_write+0x179/0x220 ntfs_inode_sync_filename+0x83d/0x1080 __ntfs_write_inode+0x1049/0x1480 ntfs_file_fsync+0x131/0x9b0 ================================================================== BUG: KASAN: slab-out-of-bounds in post_write_mst_fixup+0x1aa/0x1d0 Write of size 2 at addr ffff8881586c91fe by task p/9428 Call Trace: <TASK> dump_stack_lvl+0x100/0x190 print_report+0x139/0x4ad ? post_write_mst_fixup+0x1aa/0x1d0 ? __virt_addr_valid+0x262/0x500 ? post_write_mst_fixup+0x1aa/0x1d0 kasan_report+0xe4/0x1d0 ? post_write_mst_fixup+0x1aa/0x1d0 post_write_mst_fixup+0x1aa/0x1d0 ntfs_icx_ib_sync_write+0x179/0x220 ntfs_inode_sync_filename+0x83d/0x1080 __ntfs_write_inode+0x1049/0x1480 ntfs_file_fsync+0x131/0x9b0 ================================================================== Let's move the post_write_mst_fixup() call to ntfs_ib_write(). The ntfs_ib_write() function calls pre_write_mst_fixup() at the beginning. If the index_block contents is invalid, pre_write_mst_fixup() fails and ntfs_ib_write() returns early without calling post_write_mst_fixup() on bad index_block.
CVSS v3.1
Score 7.8high
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel NTFS driver had a vulnerability where ntfs_icx_ib_sync_write() called post_write_mst_fixup() after ntfs_ib_write() returned an error, without distinguishing between I/O errors and validation failures. Since post_write_mst_fixup() assumes valid index_block contents and does not perform boundary checks, this led to out-of-bounds memory access when the index_block was invalid. An attacker could craft a malicious NTFS image with large or malformed index_block.usa_ofs and usa_count values to trigger this memory corruption. The fix moves the post_write_mst_fixup() call into ntfs_ib_write(), preventing calls on invalid index_block data.
Potential Impact
The vulnerability causes out-of-bounds memory access in kernel space, which can lead to memory corruption. Although no specific exploit in the wild is known, this type of flaw could potentially be leveraged for denial of service or privilege escalation if exploited. The impact is limited to systems mounting or writing to malicious NTFS images.
Mitigation Recommendations
A fix has been implemented in the Linux kernel by relocating the post_write_mst_fixup() call to ntfs_ib_write(), ensuring it is only invoked after successful pre_write_mst_fixup() validation. Users should apply the updated Linux kernel version containing this fix. Patch status is not explicitly stated here; check the vendor or kernel mailing list advisories for the exact fixed kernel versions and apply updates accordingly.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-7v8v-8486-fvc6
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-64431"]
- Ecosystems
- []
- Database Specific Severity
- null
- Cvss Version
- null
Threat ID: 6a6542099c2644c7f80838c0
Added to database: 07/25/2026, 23:08:57 UTC
Last enriched: 07/25/2026, 23:24:27 UTC
Last updated: 09/07/2026, 10:52:10 UTC
Views: 39
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