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CVE-2026-72200
ntfs: detect mapping-pairs LCN accumulator overflow
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem fs/ntfs. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72200 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 | won't fix | 6.1.190-1 | Debian has decided against an update for bookworm: NTFS_FS support disabled. Moving to a newer release is the way to get the fix. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The NTFS mapping-pairs parser accumulates relative LCN deltas in a signed integer. A corrupted attribute can drive that addition past the representable range. One corrupt runlist shape sets the accumulated LCN to S64_MAX and then adds a delta of 1 in the next mapping-pairs entry. Signed overflow is undefined and can turn an invalid runlist into a different set of physical clusters. Check the LCN addition for overflow before storing the next run.
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/ntfs/runlist.c
- What this is
- NTFS FILESYSTEMMAINTAINERS section matched on fs/ntfs/ · linux-fsdevel@vger.kernel.org · Maintained
- Kernel module
- ntfs
Check it on the machine
grep -w CONFIG_NTFS_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 ntfsPrints 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 1 release. It does build it in 2 releases, so the answer depends on which release the machine runs. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookwormn
- trixie?
- forky, sidm
- n
- not enabled on any flavour - this release does not build the code
- ?
- not established - no Makefile entry for the affected file
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switch
- CONFIG_NTFS_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
- 2026-08-15 (2 months ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.65%, higher than 50.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- fs/ntfs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.12 | 6.9 | 7ffa8f3d3023 |
| 7.1 | 7.1.5 | 7fb64788812d |
| 7.1 | 7.2 | ec4f061f2219 |
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:NAttack vector, network
- Legacy NTFS is NFS-exportable (ntfs_export_ops) and commonly served via ksmbd; remote SMB/NFS reads on an exported NTFS mount reach ntfs_mapping_pairs_decompress() through VFS read/iomap and ntfs_map_runlist() without local shell access.
- AC:LAttack complexity, low
- An attacker fully controls crafted on-disk mapping pairs offline (e.g., drive LCN to S64_MAX then add +1) and can reliably trigger decompression on mount or the next attribute access that maps the runlist; no races or victim-specific layout are required.
- PR:NPrivileges required, none
- Triggering decompression needs only permission to cause server-side parsing of mounted NTFS metadata (e.g., guest/anonymous SMB or permissive NFS read, or unprivileged local open/read on an already-mounted volume), not init-namespace root or CAP_SYS_ADMIN at trigger time.
- UI:NUser interaction, none
- After the volume is mounted/exported, exploitation requires only normal remote or local filesystem read/open operations on files whose non-resident attributes carry the poisoned mapping pairs; no additional victim mount dialogs, USB insertion, or other user actions are needed during the attack.
- S:UScope, unchanged
- Impact stays within the kernel/host context (runlist corruption and misdirected block I/O on the mounted volume); it does not cross a VM, container, or IOMMU boundary to another security authority.
- C:HConfidentiality impact, high
- Signed LCN accumulator overflow (undefined behavior) yields attacker-controlled cluster mappings, so subsequent reads can be directed to arbitrary on-volume clusters and disclose other files' data and metadata beyond the accessed object.
- I:HIntegrity impact, high
- Corrupted LCN values misdirect kernel writeback and allocation I/O to arbitrary physical clusters on the volume, enabling cross-file/metadata tampering and further corruption exploitable for broader integrity compromise.
- A:HAvailability impact, high
- Misdirected cluster I/O and corrupt runlists cause mount/read/write failures, can destroy critical structures like $MFT, and repeated remote access can deny service to the host or exported filesystem.