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CVE-2026-80673
ntfs: bound the look-ahead attribute-list entry in ntfs_external_attr_find()
Published 2026-08-28 (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-2026-80673 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
When resolving an attribute lookup with a non-zero @lowest_vcn, ntfs_external_attr_find() peeks at the next $ATTRIBUTE_LIST entry to decide whether to keep searching, but bounds that not-yet-validated entry only with "(u8 *)next_al_entry + 6 < al_end" (which proves just bytes 0..6 are in range) and "(u8 *)next_al_entry + length <= al_end" with an attacker-controlled, non-8-aligned length. It then reads next_al_entry->lowest_vcn (an __le64 at offset 8) and the name at next_al_entry->name_offset, both of which can lie past al_end -- the exact end of the kvmalloc'd attribute-list buffer (allocated at the on-disk attr_list_size, no rounding). A crafted on-disk $ATTRIBUTE_LIST whose last entry sits a few bytes before al_end therefore yields a slab out-of-bounds read when the inode is read. Validate the look-ahead entry with ntfs_attr_list_entry_is_valid() (added in patch 1/3) before dereferencing lowest_vcn and the name, so the same fixed-header, length and name bounds the main attribute-list walk uses now guard this read too.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
fs/ntfs/attrib.c
- What this is
- NTFS FILESYSTEMMAINTAINERS section matched on fs/ntfs/ · linux-fsdevel@vger.kernel.org · Maintained
- Kernel module
- ntfs
Check it on the machine
grep -w CONFIG_NTFS_FS /boot/config-$(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
- 2026-08-28 (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
- 0.55%, higher than 45.0% 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 | 44885c9b45eb |
| 7.1 | 7.2 | 344b18f389f9 |
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
- Classic NTFS registers ntfs_export_ops; remote nfsd/ksmbd VFS reads/lookups on an exported crafted NTFS volume reach ntfs_attr_lookup(lowest_vcn!=0)->ntfs_external_attr_find() without local syscall access on the victim host.
- AC:LAttack complexity, low
- Attacker fully controls on-disk $ATTRIBUTE_LIST tail geometry (short look-ahead entry length/placement); weak bounds let lowest_vcn/name reads pass al_end deterministically on walks with non-zero lowest_vcn, with no race or uncontrollable layout.
- PR:NPrivileges required, none
- Per kernel CNA crafted-filesystem model, exploitation needs only supplying a malicious NTFS image (USB/automount) or read access to mounted/exported NTFS content to trigger extent lookups; no init-namespace root or CAP_SYS_ADMIN on the lookup/read path.
- UI:NUser interaction, none
- udisks2/systemd automount of removable NTFS and remote NFS/SMB reads on exported volumes reach the vulnerable attribute-list look-ahead during normal file/inode access without the victim deliberately mounting images or performing attacker-specific actions.
- S:UScope, unchanged
- Slab out-of-bounds read and possible kernel crash stay within the mounting host kernel; this is standard filesystem parsing, not a VM escape, IOMMU bypass, or cross-sandbox scope change.
- C:HConfidentiality impact, high
- Unvalidated look-ahead reads next_al_entry->lowest_vcn and the Unicode name past the kvmalloc attribute-list end (allocated at exact attr_list_size), disclosing adjacent slab heap memory beyond a few bytes.
- I:HIntegrity impact, high
- Attacker-controlled look-ahead entry fields drive kernel parsing of forged attribute-list metadata and adjacent slab contents; per CNA guidance this memory-corruption class can be leveraged for arbitrary kernel modification or control-flow hijack.
- A:HAvailability impact, high
- Slab out-of-bounds read from the attribute-list buffer during inode/extent resolution can access unmapped adjacent memory and oops or panic the kernel, fully denying availability.