# CVE-2026-98975: xfs: stop exchanging reflink flags when exchanging mappings


- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 23 Oct 2026
- **Updated:** 24 Oct 2026
- **Also known as:** AZL-110801, BELL-CVE-2026-98975, DEBIAN-CVE-2026-98975, GHSA-pxhv-6mjw-34j3, UBUNTU-CVE-2026-98975

## What is CVE-2026-98975?

CVE-2026-98975 is a high-severity vulnerability in Linux, published on 23 Oct 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

xfs: stop exchanging reflink flags when exchanging mappings

When an exchange covers both files from offset 0 to i_disk_size,
xmi_can_exchange_reflink_flags() assumes every mapping moved and hands
the reflink flag over to the other file.

That assumption is wrong.  A file can still own shared blocks past
i_disk_size, e.g. after EXCHANGE_RANGE_TO_EOF sets a smaller size
without unmapping anything.  The flag is cleared anyway, and the next
write to such a block happens in place instead of CoW, corrupting the
other file that shares it.

Commit a23eca88448e ("xfs: fix exchange-range reflink flag clearing
issue with INO1_WRITTEN") fixed one instance of this.  Rather than add
another special case, stop moving the flags.
xfs_exchmaps_ensure_reflink() already sets the flag on both inodes
before the exchange, so both just keep it.

Nothing sets CLEAR_INO{1,2}_REFLINK anymore.  Intents logged by older
kernels may still carry them; recovery already masks them off, so they
stay in the log format mask and are ignored.

XFS_IOC_SWAPEXT has the same problem: it moves the reflink flag from
one inode to the other along with the extents.  Just removing that is
not enough here: the exchange path flags both inodes up front in
xfs_exchmaps_ensure_reflink(), but swapext has no such step, so the
inode receiving the shared extents would be left without the flag.
Set it on both inodes instead, and make sure both have a CoW fork,
since an inode with the reflink flag is expected to have one.

The flag now stays until FALLOC_FL_UNSHARE_RANGE, xfs_scrub, or a
truncate to zero removes it.

## Which versions are affected by CVE-2026-98975?


## How do I fix CVE-2026-98975?

Upgrade to a fixed version.

## Is CVE-2026-98975 being exploited?

There is no known exploitation of CVE-2026-98975 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98975 and fix it if it is affected.

What it is: CVE-2026-98975 is a high-severity vulnerability in Linux, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-98975 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98975/ (Markdown: https://insights.sbomify.com/CVE-2026-98975/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98975
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98975
- OSV: https://osv.dev/vulnerability/CVE-2026-98975

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98975/
Summaries are generated and may contain mistakes; the official description above is the record.