Answer in brief
CVE-2026-64431 records a Unknown severity vulnerability in ntfs: avoid calling post_write_mst_fixup() for invalid index_block. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=0a8ac0c1fa0b99a5b29002bc7f232ed7eafddef0 <e2018628301a6d9f54e34b0cb417f1688c66df1d || >=0a8ac0c1fa0b99a5b29002bc7f232ed7eafddef0 <5b6eedd7cc2936f9238e852b553a1b326105bde8 | e2018628301a6d9f54e34b0cb417f1688c66df1d, 5b6eedd7cc2936f9238e852b553a1b326105bde8 |
| Linux/Linuxgeneric | 7.1 | Not reported |
Published upstream
Jul 25, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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.
Quoted source text, attributed separately from HOL analysis.
Answer in brief
CVE-2026-64431 records a Unknown severity vulnerability in ntfs: avoid calling post_write_mst_fixup() for invalid index_block. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=0a8ac0c1fa0b99a5b29002bc7f232ed7eafddef0 <e2018628301a6d9f54e34b0cb417f1688c66df1d || >=0a8ac0c1fa0b99a5b29002bc7f232ed7eafddef0 <5b6eedd7cc2936f9238e852b553a1b326105bde8 | e2018628301a6d9f54e34b0cb417f1688c66df1d, 5b6eedd7cc2936f9238e852b553a1b326105bde8 |
| Linux/Linuxgeneric | 7.1 | Not reported |
Published upstream
Jul 25, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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.
Quoted source text, attributed separately from HOL analysis.