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CVE-2026-89782
fs/ntfs3: reject restart table growth beyond U16_MAX entries
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-2026-89782 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
During $LogFile replay, log_replay() indexes the transaction table by the transact_id taken from the log record header. check_log_rec() only verifies that transact_id is non-zero and properly aligned, not its magnitude, so a crafted image can request an arbitrarily large index. alloc_rsttbl_from_idx() grows the table to cover that index via extend_rsttbl(), which passes the new entry count to init_rsttbl(): rt = init_rsttbl(esize, used + add); used + add is computed as u32 but init_rsttbl() takes a u16, and the count is stored in struct RESTART_TABLE as a __le16. When used + add exceeds U16_MAX it is truncated, init_rsttbl() allocates a table far smaller than the index requires, and alloc_rsttbl_from_idx() then dereferences and writes at the original, untruncated offset -- an out-of-bounds access past the allocation, reachable by mounting a crafted NTFS image. BUG: KASAN: use-after-free in alloc_rsttbl_from_idx (fs/ntfs3/fslog.c:950) Read of size 4 at addr ffff8880327ffff8 by task exploit alloc_rsttbl_from_idx (fs/ntfs3/fslog.c:950) log_replay (fs/ntfs3/fslog.c:4562) ntfs_loadlog_and_replay (fs/ntfs3/fsntfs.c:324) ntfs_fill_super (fs/ntfs3/super.c:1393) get_tree_bdev_flags vfs_get_tree path_mount __x64_sys_mount A restart table is limited to U16_MAX entries by its __le16 count, so a larger growth request is invalid input. Reject it in extend_rsttbl(); all callers already handle a NULL return.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
fs/ntfs3/fslog.c
- What this is
- NTFS3 FILESYSTEMMAINTAINERS section matched on fs/ntfs3/ · ntfs3@lists.linux.dev · Supported
- Kernel module
- ntfs3
Check it on the machine
grep -w CONFIG_NTFS3_FS /boot/config-$(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 7.0% 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 | caa0ec3fc44a |
| 5.15 | 6.1.188 | 339e59996ff1 |
| 5.15 | 6.6.157 | ecde45cd81dc |
| 5.15 | 6.12.110 | be218a01aadf |
| 5.15 | 6.18.52 | aad605a45061 |
| 5.15 | 7.2.6 | 967a5ff8a614 |
| 5.15 | 7.3 | 111f8d74a19d |
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 bug is reached only while mounting a local NTFS block or loop device: path_mount → ntfs_fill_super → ntfs_loadlog_and_replay → log_replay → alloc_rsttbl_from_idx. ksmbd/nfsd never parse $LogFile; journal replay runs at fill_super, not while serving exported files.
- AC:LAttack complexity, low
- The attacker fully controls on-disk $LogFile LFS_RECORD_HDR.transact_id. check_log_rec() only requires it non-zero and TRANSACTION_ENTRY-aligned, so a crafted index with used+add > U16_MAX truncates init_rsttbl() and hits the OOB access deterministically on mount 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 to trigger the overflow.
- S:UScope, unchanged
- Heap out-of-bounds access and use-after-free occur 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
- After the truncated allocation, alloc_rsttbl_from_idx() reads a restart-table word at the original untruncated transact_id offset (KASAN use-after-free). That attacker-chosen heap index plus UAF of the freed old table enable arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- extend_rsttbl() memcpy's the old table into a truncated kmalloc buffer, then alloc_rsttbl_from_idx() memset's and writes RESTART_ENTRY_ALLOCATED at the untruncated offset, producing an OOB/UAF heap write that can corrupt adjacent slab objects for control-flow hijacking.
- A:HAvailability impact, high
- KASAN reported use-after-free in alloc_rsttbl_from_idx() on mount of a crafted NTFS image; the out-of-bounds heap access during log replay can oops or panic the kernel and is repeatable on every mount of the malicious volume.