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CVE-2026-72195
fs/ntfs3: bound attr_off in UpdateResidentValue against data_off
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-2026-72195 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 do_action()'s UpdateResidentValue case (fslog.c:3307), lrh->attr_off and lrh->redo_len come from the on-disk LRH. When they satisfy aoff + dlen < attr->res.data_off, the assignment attr->res.data_size = cpu_to_le32(aoff + dlen - data_off); underflows to ~4 GiB (e.g. 0xFFFFFFF9 when aoff=0x10, dlen=1, data_off=0x18). Subsequent code that reads attr->res.data_size to walk the resident attribute payload would then read up to 4 GiB past the 1024-byte MFT record allocation. The existing mi_enum_attr() defense in fs/ntfs3/record.c:287 catches the corrupted data_size on the next attribute walk and fails the mount, but only on the path that walks all attributes. A read site that picks an attribute by name and reads its data_size without re-validating is not covered. Validate aoff against data_off and asize at the source. Reproduced under UML+KASAN on mainline 8d90b09e6741 via pr_warn-only probe: with aoff=0x10 and data_off=0x18, the post-assignment data_size is 0xfffffff9 (mount then fails at -22 from mi_enum_attr). [almaz.alexandrovich@paragon-software.com: clang-formatted the changes]
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
- 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 5.8% 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 | 5.15.212 | ab8761676d63 |
| 5.15 | 6.1.178 | 53c12f178f58 |
| 5.15 | 6.6.145 | 546518468e6c |
| 5.15 | 6.12.97 | 97758fd9756b |
| 5.15 | 6.18.40 | 50b5e83384e7 |
| 5.15 | 7.1.5 | a89c66674283 |
| 5.15 | 7.2 | d1570c48f49a |
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 bug is reached only when the kernel mounts an attacker-controlled NTFS volume and replays $LogFile via ntfs_loadlog_and_replay→log_replay→do_action(UpdateResidentValue); exploitation uses the local mount syscall on a block/loop device, not a network-facing kernel service.
- AC:LAttack complexity, low
- The attacker fully controls malicious on-disk LRH fields (attr_off, redo_len, data) in $LogFile; triggering the data_size underflow is deterministic once the crafted volume is mounted, with no races or conditions outside attacker control.
- PR:LPrivileges required, low
- Mounting ntfs3 requires CAP_SYS_ADMIN in the mount namespace; an unprivileged local attacker can obtain this via user namespaces (unshare -Ur) and loop-mount a crafted NTFS image, without real root in the initial user namespace.
- UI:NUser interaction, none
- No victim interaction is required when the attacker mounts their own malicious NTFS image in a user namespace; exploitation does not depend on another user plugging in media, opening a file, or performing an additional action.
- S:UScope, unchanged
- The vulnerability corrupts kernel heap metadata during filesystem journal replay on the mounting host; impact stays within the kernel's security authority and does not constitute a VM escape, sandbox escape, or cross-authority boundary change.
- C:HConfidentiality impact, high
- Unsigned underflow sets attr->res.data_size to ~4 GiB; subsequent resident-attribute consumers that trust data_size can read far beyond the ~1 KiB kmalloc MFT record allocation, disclosing adjacent kernel heap memory.
- I:HIntegrity impact, high
- The underflow corrupts resident-attribute metadata and UpdateResidentValue memmove paths using attacker-controlled offsets can overwrite attribute headers and drive out-of-bounds writes during replay, enabling heap corruption suitable for control-flow hijacking.
- A:HAvailability impact, high
- Malformed journal replay can trigger kernel faults (KASAN/oops) or abort mount; repeated mount attempts against the malicious image cause persistent denial of service on the affected system.