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CVE-2026-72202
ntfs: avoid heap allocation for free-cluster readahead state
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-2026-72202 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| 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
get_nr_free_clusters() allocates a temporary file_ra_state before it publishes the precomputed free cluster count, sets NVolFreeClusterKnown(), and wakes vol->free_waitq. If that allocation fails, the worker returns without setting the flag or waking waiters, so callers waiting for the free count can block indefinitely. The readahead state is only used synchronously while scanning the bitmap. Keep it on the stack and pass it by address to the readahead helper. This eliminates the early allocation failure path instead of adding a special case that publishes a conservative count and wakes the waitqueue. Zero-initialize the on-stack state because file_ra_state_init() only sets ra_pages and prev_pos. Apply the same treatment to __get_nr_free_mft_records(), which scans the MFT bitmap with the same short-lived readahead state.
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/super.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
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.49%, higher than 40.6% 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 |
|---|---|---|
| 7.1 | 7.1.5 | 40ee64e633e5 |
| 7.1 | 7.2 | c05132077df5 |
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
- fs/ntfs registers ntfs_export_ops; on servers with an rw-mounted NTFS volume exported via nfsd or ksmbd, remote NFS/SMB statfs, write, and fallocate RPCs reach ntfs_statfs, ntfs_fallocate, and iomap allocation paths that block on vol->free_waitq when precalc never publishes NVolFreeClusterKnown.
- AC:LAttack complexity, low
- A local attacker can hold the system under GFP_NOFS memory pressure across NTFS mount so the tiny file_ra_state kzalloc in precalc_free_clusters fails; once that broken state exists, any statfs/write/fallocate caller deterministically enters wait_event without races or victim-specific layout.
- PR:NPrivileges required, none
- Exploitation at trigger time needs only access to the mounted/exported NTFS volume (e.g., remote NFS/SMB statfs or write permission); no CAP_SYS_ADMIN, root, or init-namespace privileges are required on the server to hit the indefinite waitqueue block.
- UI:NUser interaction, none
- After an administrator has rw-mounted and optionally exported the NTFS volume (or automounted dual-boot/shared storage), attackers drive normal statfs or write operations that hang on free_waitq; no per-attack victim clicks, opens, or cooperative actions are required beyond that standing configuration.
- S:UScope, unchanged
- Impact is indefinite blocking of kernel threads serving the affected NTFS volume within the host kernel security authority; this is standard filesystem denial of service, not a VM escape, container breakout, or IOMMU boundary bypass.
- C:NConfidentiality impact, none
- The bug is a missing wake on kzalloc failure in get_nr_free_clusters; it does not corrupt memory, read out of bounds, or use-after-free, and provides no kernel pointer leak or arbitrary memory disclosure primitive.
- I:NIntegrity impact, none
- Failed precalc leaves free-cluster accounting unpublished and stalls I/O waiters; it does not modify on-disk NTFS metadata or in-memory file contents beyond denying forward progress to blocked callers.
- A:HAvailability impact, high
- After precalc aborts without NVolSetFreeClusterKnown or wake_up_all, wait_event(vol->free_waitq, NVolFreeClusterKnown) never completes, permanently hanging statfs, writes, fallocate, and cluster alloc/free paths (D-state), including nfsd/ksmbd worker threads serving the export.