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CVE-2026-74570
ntfs: harden runlist realloc size calculations
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-2026-74570 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 | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Add a shared helper to safely convert runlist element counts to byte sizes using overflow checks, and use it in both ntfs_rl_realloc() and ntfs_rl_realloc_nofail().
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
- 0.55%, 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 | 7.1.8 | 57e7b8bf7b02 |
| 7.1 | 7.2 | 8bed376124ab |
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
- Crafted NTFS metadata is parsed when remote clients read files on NFS- or SMB-exported NTFS mounts (ntfs_export_ops); nfsd/ksmbd VFS reads reach ntfs_mapping_pairs_decompress/ntfs_runlists_merge and the vulnerable ntfs_rl_realloc path without local shell access.
- AC:LAttack complexity, low
- An attacker can deterministically craft NTFS mapping pairs or runlist merge sizes to force int overflow in realloc byte calculations; no races, rare configs, or victim-specific heap layout are required to trigger the undersized alloc and oversized memcpy.
- PR:NPrivileges required, none
- Triggering the bug requires only access to mounted NTFS content (e.g., NFS/SMB read of an exported share or loop-mount in a user namespace with CAP_SYS_ADMIN), not real init-namespace root; no Linux superuser credentials are needed on the read/decompress code path.
- UI:NUser interaction, none
- Exploitation needs no victim interaction beyond the attacker or a remote client issuing normal filesystem reads/opens on crafted NTFS metadata; no mount dialog, USB insertion, or other user action by a separate victim is required.
- S:UScope, unchanged
- Impact is confined to kernel memory corruption and privilege escalation within the same kernel security domain; it does not cross VM, container, or IOMMU boundaries to affect a separate authority.
- C:HConfidentiality impact, high
- Integer-overflowed memcpy copies far beyond the undersized kvzalloc/kvmalloc buffer, corrupting adjacent kernel heap objects and enabling arbitrary kernel memory disclosure when leveraged for exploitation.
- I:HIntegrity impact, high
- The heap buffer overflow provides a strong arbitrary kernel write primitive via adjacent-object corruption and heap grooming, sufficient for control-flow hijacking and local privilege escalation.
- A:HAvailability impact, high
- Corrupting kernel heap metadata reliably causes kernel oops/panic or forced reboot; even failed exploitation attempts typically crash the host, and successful exploitation can hang or kill the system.