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CVE-2026-72196
fs/ntfs3: bound copy_lcns dp->page_lcns[] index in analysis pass
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem fs/ntfs3. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72196 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 | fixed | 6.1.180-1 | Update the kernel and reboot. Fixed in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| 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
In log_replay()'s analysis pass, after find_dp() returns a valid DIR_PAGE_ENTRY for the (target_attr, target_vcn) tuple, the copy_lcns block walks lrh->lcns_follow further entries: t16 = le16_to_cpu(lrh->lcns_follow); for (i = 0; i < t16; i++) { size_t j = (size_t)(le64_to_cpu(lrh->target_vcn) - le64_to_cpu(dp->vcn)); dp->page_lcns[j + i] = lrh->page_lcns[i]; } find_dp() only validates that target_vcn falls within [dp->vcn, dp->vcn + dp->lcns_follow), i.e., that the FIRST cluster is covered. The walk through the further entries is not bounded against dp->lcns_follow. For a malformed LRH where target_vcn = dp->vcn + dp->lcns_follow - 1 and lrh->lcns_follow > 1, the i > 0 writes overflow the dp's allocated page_lcns[] array. Add the missing j + lrh->lcns_follow <= dp->lcns_follow guard. Reproduced under UML+KASAN on mainline 8d90b09e6741 as a slab-out-of-bounds write of size 8 from log_replay+0x68d4 on the mount path. This is distinct from Pavitra Jha's 2026-05-02 patch ("fs/ntfs3: validate lcns_follow in log_replay conversion", <20260502154252.164586-1-jhapavitra98@gmail.com>) which addresses the separate version-0 dirty-page-table conversion path's memmove(&dp->vcn, ...) call. The two fixes are complementary; both should land. [almaz.alexandrovich@paragon-software.com: clang-formatted the changes, fixed conflicts]
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/ntfs3/fslog.c
- What this is
- NTFS3 FILESYSTEMMAINTAINERS section matched on fs/ntfs3/ · ntfs3@lists.linux.dev · Supported
- Kernel module
- ntfs3
Check it on the machine
grep -w CONFIG_NTFS3_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 ntfs3Prints 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 3 releases. It does build it in 1 release, so the answer depends on which release the machine runs.
- bookwormn
- trixiem
- forky, sidn
- n
- not enabled on any flavour - this release does not build the code
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_NTFS3_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
- 8.4 high
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.18%, higher than 7.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/ntfs3
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.15 | 6.1.178 | 9b3d8cc9d54f |
| 5.15 | 6.6.145 | 9b7c28d8c61b |
| 5.15 | 6.12.97 | 0f13e823bf86 |
| 5.15 | 6.18.40 | d240cd98f5f7 |
| 5.15 | 7.1.5 | 49c86dae0c0c |
| 5.15 | 7.2 | 5e7b598660cf |
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 flaw is in ntfs3 log_replay() during mount when parsing a crafted $LogFile on a block device; exploitation requires a local mount syscall or auto-mount of attacker-supplied removable media, not delivery through a network-facing kernel protocol handler.
- AC:LAttack complexity, low
- An attacker fully controls malicious NTFS $LogFile journal fields (target_vcn, lcns_follow, page_lcns) and can craft the dirty-page-table state; KASAN reliably reproduced the slab OOB write on mount with no races or attacker-uncontrollable conditions.
- PR:NPrivileges required, none
- No account or privileges on the victim are needed when a crafted NTFS volume on removable media is auto-mounted by udisks/systemd as root; alternatively an unprivileged user can trigger replay via user-namespace mount with CAP_SYS_ADMIN.
- UI:NUser interaction, none
- Once an attacker mounts or causes mount of a crafted NTFS image, log_replay() runs automatically inside ntfs_fill_super() with no further user interaction; the vulnerable copy_lcns path is reached during standard journal analysis on every affected mount attempt.
- S:UScope, unchanged
- Exploitation corrupts kernel heap memory during ntfs3 journal replay in the mounting process context; impact is privilege escalation within the same kernel/host security boundary, not a VM-guest-to-host or IOMMU boundary crossing.
- C:HConfidentiality impact, high
- KASAN confirmed a slab out-of-bounds write of 8 bytes past dp->page_lcns[] in a kmalloc-backed DIR_PAGE_ENTRY; such heap corruption can overwrite adjacent slab objects and be groomed into arbitrary kernel memory read primitives.
- I:HIntegrity impact, high
- The bug is an out-of-bounds write into kernel heap metadata or adjacent objects beyond the allocated page_lcns[] array; per kernel guidance OOB writes enable controlled heap corruption paths toward arbitrary kernel writes and privilege escalation.
- A:HAvailability impact, high
- KASAN reported slab-out-of-bounds write from log_replay() on mount; heap corruption during journal replay can cause immediate kernel oops/panic and is repeatable on each mount of a malicious NTFS volume, constituting high availability impact.