CVE-2026-53027

What the bug is

When a compressed or sparse attribute has its clusters frame-aligned, vcn is rounded down to the frame start using cmask, which can result in vcn != vcn0. In this case, vcn and vcn0 may reside in different attribute segments. The code already handles the case where vcn is in a different segment by loading its runs before allocation. However, it fails to load runs for vcn0 when vcn0 resides in a different segment than vcn. This causes run_lookup_entry() to return SPARSE_LCN for vcn0 since its segment was never loaded into the in-memory run list, triggering the WARN_ON(1). Fix this by adding a missing check for vcn0 after the existing vcn segment check. If vcn0 falls outside the current segment range [svcn, evcn1), find and load the attribute segment containing vcn0 before performing the run lookup. The following scenario triggers the bug: attr_data_get_block_locked() vcn = vcn0 & cmask <- vcn != vcn0 after frame alignment load runs for vcn segment <- vcn0 segment not loaded! attr_allocate_clusters() <- allocation succeeds run_lookup_entry(vcn0) <- vcn0 not in run -> SPARSE_LCN WARN_ON(1) <- bug fires here!

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/attrib.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 ntfs3

Prints 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 2 releases, so the answer depends on which release the machine runs.

• bookwormn
• trixiem
• forky, sidn
• bookworm · linux-6.12m

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

2026-06-24 (4 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.12%, higher than 1.8% 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
6.2	6.6.145	ea59d9dbc550
6.2	6.12.96	d68a14450783
6.2	6.18.39	08fad5d5a26c
6.2	7.0.10	2b4ae1ce613a
6.2	7.1	d7ea8495fd30
6.1.132	0	0

Debian advisories