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CVE-2026-72210
ntfs: fix off-by-one in mapping pairs decoding bounds checks
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-2026-72210 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
In ntfs_mapping_pairs_decompress(), attr_end points one byte past the end of the attribute record: attr_end = (u8 *)attr + le32_to_cpu(attr->length); The two bounds checks validating that mapping pair data bytes fit within the attribute use strict greater-than (>), which allows a one-byte out-of-bounds read when the data extends exactly to attr_end: b = *buf & 0xf; if (b) { if (unlikely(buf + b > attr_end)) // off-by-one goto io_error; for (deltaxcn = (s8)buf[b--]; b; b--) deltaxcn = (deltaxcn << 8) + buf[b]; } When buf + b == attr_end, the check evaluates to false and buf[b] reads one byte past the valid attribute boundary. The same pattern appears in the LCN delta bytes check. Fix both checks to use >= so that buf[b] at exactly attr_end is correctly rejected as out of bounds.
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 | 7.1.5 | bfe835e535fe |
| 7.1 | 7.2 | 18760a74ef7c |
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
- The legacy NTFS driver is exported via nfsd and commonly shared over ksmbd; remote NFS/SMB reads on an NTFS-backed export reach ntfs_mapping_pairs_decompress() through VFS read/iomap and ntfs_map_runlist() without further local access.
- AC:LAttack complexity, low
- An attacker fully controls a crafted NTFS image offline and can place mapping pairs to hit the exact off-by-one boundary, reliably triggering the flaw on mount or on the next access that decompresses that attribute extent.
- PR:NPrivileges required, none
- Exploitation needs only the ability to trigger server-side parsing of the mounted volume (e.g., guest/anonymous SMB or permissive NFS export); no init-namespace root or CAP_SYS_ADMIN on the victim is required at trigger time.
- UI:NUser interaction, none
- After an administrator mounts the poisoned volume, a remote client can trigger the bug with protocol read/open operations alone; no additional end-user clicks, plug-in events, or mount actions are needed during exploitation.
- S:UScope, unchanged
- Impact stays within kernel/host context (metadata parsing, runlist corruption, and resulting I/O); it does not cross a VM, container, or IOMMU security boundary to another authority.
- C:HConfidentiality impact, high
- The flawed bounds check permits a one-byte out-of-bounds kernel read past the attribute end, often into MFT record slack that may contain stale cached data, matching OOB-read disclosure impact.
- I:HIntegrity impact, high
- The leaked byte is folded into runlist length/LCN deltas, yielding attacker-influenced cluster mappings that can misdirect subsequent kernel block I/O and corrupt arbitrary on-volume metadata or file data.
- A:HAvailability impact, high
- Corrupt runlists and failed decompression paths surface as ntfs_error/EIO during mount or I/O and can panic or wedge the node under repeated remote access, giving a practical denial-of-service.