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CVE-2026-63793
ntfs: serialize volume label accesses
Published 2026-07-19 (3 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-2026-63793 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 | not affected | 7.2.11-1 | Nothing to do. forky never shipped the vulnerable code. |
| Debian unstablesid | not affected | 7.2.11-1 | Nothing to do. sid never shipped the vulnerable code. |
The vulnerability
What the bug is
Protect vol->volume_label with a mutex and snaphost the label before copy_to_user. This prevent a use-after-free when FS_IOC_SETFSLABEL replaces the vol->volume_label and FS_IOC_GETTSLABEL reads it concurrently.
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/file.c
fs/ntfs/super.c
fs/ntfs/volume.h
- 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
- 2026-07-19 (3 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.3% 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 | 7.1.3 | acd744019460 |
| 7.1 | 7.2 | e9e50ce4f13d |
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 vulnerability is reached only through the local ioctl(2) syscall on an open file or directory on a mounted legacy NTFS (fs/ntfs) volume; there is no network-facing code path to these handlers.
- AC:LAttack complexity, low
- An attacker controls both sides of the race by concurrently issuing FS_IOC_SETFSLABEL and FS_IOC_GETFSLABEL from separate threads or file descriptors, making the use-after-free reliably triggerable without conditions outside attacker control.
- PR:LPrivileges required, low
- Exploitation requires CAP_SYS_ADMIN to call FS_IOC_SETFSLABEL (which performs the kfree), but that capability is obtainable by an unprivileged user via user namespaces or privileged containers, and mounting NTFS for ioctl access does not require init-namespace root.
- UI:NUser interaction, none
- No victim interaction is required; the attacker opens a file on the NTFS mount and races the label get/set ioctls themselves, including on auto-mounted dual-boot or shared-workstation NTFS partitions.
- S:UScope, unchanged
- The use-after-free corrupts kernel heap memory within the same kernel security authority and does not cross VM, container, or IOMMU boundaries on its own.
- C:HConfidentiality impact, high
- The bug is a kmalloc use-after-free where the read path calls strlen() and copy_to_user() on freed memory, enabling disclosure of adjacent heap contents to userspace and supporting further info-leak primitives.
- I:HIntegrity impact, high
- Use-after-free on a kmalloc-allocated volume label string is a standard heap corruption primitive that can be groomed for arbitrary kernel memory writes and potential privilege escalation or code execution.
- A:HAvailability impact, high
- Concurrent access to the freed label pointer can cause kernel oopses or panics during strlen() or copy_to_user(), and UAF corruption inherently threatens system availability even before full exploitation.