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CVE-2026-89781
fs/ntfs3: fix out-of-bounds read in read_log_rec_buf()
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem fs/ntfs3. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89781 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
read_log_rec_buf() copies a log record into a caller buffer starting at u32 off = lsn_to_page_off(log, lsn) + log->record_header_len; log->record_header_len (and log->data_off, used for the following pages) comes verbatim from the on-disk restart area and is only checked for 8-byte alignment in is_rst_area_valid(), so off can exceed log->page_size. "tail = log->page_size - off" then underflows and memcpy() reads past the page_size-sized buffer returned by read_log_page(), spilling adjacent slab memory into the replay buffer. This is reachable by mounting a crafted NTFS image: BUG: KASAN: slab-out-of-bounds in read_log_rec_buf+0x216/0x580 Read of size 64 at addr ffff88800a877ff8 by task exploit/127 read_log_rec_buf fs/ntfs3/fslog.c:2299 log_replay fs/ntfs3/fslog.c:4216 ntfs_loadlog_and_replay fs/ntfs3/fsntfs.c:324 ntfs_fill_super fs/ntfs3/super.c:1392 get_tree_bdev_flags fs/super.c:1694 __x64_sys_mount fs/namespace.c:4360 The buggy address is located 4088 bytes to the right of the 4096-byte region [ffff88800a876000, ffff88800a877000) Reject an in-page offset outside the current page before the copy. [almaz.alexandrovich@paragon-software.com: replaced the >= sign with >]
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
fs/ntfs3/fslog.c
- What this is
- NTFS3 FILESYSTEMMAINTAINERS section matched on fs/ntfs3/ · ntfs3@lists.linux.dev · Supported
- Kernel module
- ntfs3
Check it on the machine
grep -w CONFIG_NTFS3_FS /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w ntfs3Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian does not build this code in 3 releases. It does build it in 2 releases, so the answer depends on which release the machine runs.
- bookwormn
- trixiem
- forky, sidn
- bookworm · linux-6.12m
- n
- not enabled on any flavour - this release does not build the code
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_NTFS3_FS
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-16 (33 days ago)source
- CVSS
- 8.4 high
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.18%, higher than 7.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/ntfs3
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.15 | 5.15.221 | df099bfdb577 |
| 5.15 | 6.1.188 | 1b2d31f1083b |
| 5.15 | 6.6.157 | 700973cc65db |
| 5.15 | 6.12.110 | 49f7cbc902b0 |
| 5.15 | 6.18.52 | 74a83aa05f73 |
| 5.15 | 7.2.6 | 53e56f7aa1d0 |
| 5.15 | 7.3 | de603b9d377f |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The OOB read is reached only while mounting a local NTFS volume (path_mount→ntfs_fill_super→ntfs_loadlog_and_replay→log_replay→read_rst_area/find_log_rec→read_log_rec_buf). ksmbd/nfsd never parse $LogFile; journal replay runs at fill_super, not while serving exported files.
- AC:LAttack complexity, low
- rec_hdr_len and data_off in the on-disk restart area are attacker-controlled and only checked for 8-byte alignment, so off=lsn_to_page_off()+record_header_len (and later data_off) can exceed page_size. The u32 tail underflow and memcpy past the kmalloc(page_size) log page are deterministic with no race.
- PR:NPrivileges required, none
- No account or privilege on the victim is required: a crafted NTFS volume on USB/removable media, a disk image, or shared storage is sufficient for udisks2/systemd automount or an administrator mount to run $LogFile replay as root.
- UI:NUser interaction, none
- Desktop, kiosk, automotive, and shared-workstation automounters mount attacker-supplied NTFS media and run log_replay() inside ntfs_fill_super() without the user opening files or confirming a dialog; attaching the crafted volume is sufficient.
- S:UScope, unchanged
- The slab out-of-bounds read occurs in the host kernel during ntfs3 journal replay in the mounting process; impact stays within one kernel security authority and is not a VM escape or IOMMU/DMA bypass.
- C:HConfidentiality impact, high
- memcpy() copies attacker-chosen client_data_len bytes from past the page_size log-page slab into the replay buffer, spilling adjacent heap. client_data_len is only bounded by kmalloc success on the restart-area path, so this is an unbounded heap OOB read (Confidentiality High), not a few-byte leak.
- I:HIntegrity impact, high
- With a valid rec_hdr_len and oversized data_off, multi-page log records keep an attacker-controlled LOG_REC_HDR then fill the rest from adjacent slab (including same-size log pages from the crafted image). do_action then memmove()s that buffer into kmalloc'd MFT and index objects, yielding kernel writes from attacker-influenced heap contents.
- A:HAvailability impact, high
- An oversized rec_hdr_len or data_off plus a large client_data_len drives memcpy() far past the 4KiB log-page allocation into unmapped slab or guard pages, causing a kernel oops or panic on mount. The crash is repeatable on every mount of the crafted NTFS volume.