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CVE-2026-80530
xfs: fix exchange-range reflink flag clearing issue with INO1_WRITTEN
Published 2026-08-26 (2 months ago) by the Linux kernel CNA. Subsystem fs/xfs. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-80530 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 | fixed | 6.12.105-1 | Update the kernel and reboot. Fixed in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.10-1 | Update the kernel and reboot. Fixed in 7.1.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.10-1 | Update the kernel and reboot. Fixed in 7.1.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When exchanging two full-file ranges, xmi_can_exchange_reflink_flags() can move the reflink inode flag from the file that currently has it to the other file, as long as exactly one side is marked. This assumes that the file contents, and therefore all shared extents, are exchanged. That assumption is not true when XFS_EXCHMAPS_INO1_WRITTEN is set. xfs_exchmaps_can_skip_mapping() can skip hole and unwritten mappings from file1, so an exchange can complete without moving every mapping that the earlier flag-swap decision accounted for. In that case the post-operation cleanup can clear the reflink flag from an inode that still owns shared written extents. Later writes then take the non-reflink write path and may update blocks that should still have been protected by CoW, which shows up as data corruption between reflink-related files. Fix this by disabling the reflink flag exchange whenever XFS_EXCHMAPS_INO1_WRITTEN is requested. The contents exchange can still proceed; the conservative outcome is that both inodes keep the reflink flag. The regular reflink flag cleanup path can drop the extra flag later once the inode no longer has shared extents.
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/xfs/libxfs/xfs_exchmaps.c
- What this is
- XFS FILESYSTEMMAINTAINERS section matched on fs/xfs/ · linux-xfs@vger.kernel.org · Supported
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid, bookworm · linux-6.12?
- ?
- not established - no Makefile entry for the affected file
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.
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
Signals
- Published
- 2026-08-26 (2 months ago)source
- CVSS
- 7.1 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Nsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- fs/xfs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.10 | 6.12.105 | 2efbd8890b53 |
| 6.10 | 6.18.46 | 0f27b22343b6 |
| 6.10 | 7.1.10 | 03c9c9116e6d |
| 6.10 | 7.2 | b2d5a81dae38 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
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 only reachable via xfs_ioc_exchange_range()/xfs_ioc_commit_range() through XFS_IOC_EXCHANGE_RANGE or XFS_IOC_COMMIT_RANGE ioctl on open XFS file descriptors; there is no nfsd, ksmbd, or network packet path to xfs_exchmaps_clear_reflink().
- AC:LAttack complexity, low
- A local attacker can craft reflinked files with hole/unwritten mappings, open both files read-write, and call exchange-range with XFS_EXCHANGE_RANGE_FILE1_WRITTEN|TO_EOF to deterministically skip mappings and trigger incorrect post-op reflink-flag clearing.
- PR:LPrivileges required, low
- XFS_IOC_EXCHANGE_RANGE has no CAP_SYS_ADMIN gate and only requires DAC write on both exchanged files plus read access to reflink-clone a victim file; unprivileged users on shared multi-tenant XFS mounts meet this without init-namespace root.
- UI:NUser interaction, none
- Exploitation requires only the attacker's own ioctl calls on files they control; no separate victim must mount media, click prompts, or perform actions beyond storing readable data the attacker reflinks.
- S:UScope, unchanged
- Impact is on-disk data corruption or commingling between reflink-linked files within the same host kernel/filesystem authority; it does not cross VM, container network, or IOMMU boundaries like a hypervisor escape.
- C:HConfidentiality impact, high
- Clearing the reflink inode flag while shared written extents remain breaks CoW isolation, so subsequent non-reflink writes can commingle or overwrite blocks still linked to other users' reflink clones, leaking data CoW should have kept private.
- I:HIntegrity impact, high
- After the incorrect reflink-flag clear, writes take the non-reflink path and directly modify shared storage blocks, letting an attacker corrupt content in other users' reflink-linked files without write permission to those inodes.
- A:NAvailability impact, none
- The failure is logical metadata mishandling causing cross-file data corruption; it does not trigger kernel oops, panic, BUG_ON, or hang, and the fix commit describes only data corruption between reflink-related files, not system unavailability.