---
id: CVE-2026-64600
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  xfs: resample the data fork mapping after cycling ILOCK

  xfs_reflink_fill_{cow_hole,delalloc} are both presented with an inode,
  a data fork mapping, and a cow fork mapp…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  xfs: resample the data fork mapping after cycling ILOCK

  xfs_reflink_fill_{cow_hole,delalloc} are both presented with an inode,
  a data fork mapping, and a cow fork mapp…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
published: '2026-07-23'
updated: '2026-07-27'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-64600'
references:
  - url: 'https://cdn2.qualys.com/advisory/2026/07/22/RefluXFS.txt'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/206c09b04dc5469c7ff14d8aceff2d47c88078d9'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/2f4acd0fcd862e22eab45690ec2c08c80b6ef2e7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/44f891bc088958399eec27f7604928694aa35581'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/50f0012da1040f69a4e788cd9aed587c9a04983f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b8c9aa832b52680ee40d6cab0efb081f9a69df05'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/dc11be133efca5fe3a2fb02b016dee825cc12f18'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e705d81a7193dd19e69b8e2bad4696d78a4ea075'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'http://www.openwall.com/lists/oss-security/2026/07/22/14'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://www.openwall.com/lists/oss-security/2026/07/22/18'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://www.openwall.com/lists/oss-security/2026/07/22/19'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
  - exploit-available
epss: 0.00158
epssPercentile: 0.04132
ingestedAt: '2026-07-27T06:16:48.977Z'
exploits:
  github: 9
  githubRepos:
    - 'https://github.com/0xBlackash/CVE-2026-64600'
    - 'https://github.com/Debajyoti0-0/CVE-2026-64600'
    - 'https://github.com/litosmartin/CVE-2026-64600-Refluxfs-PoC'
  checkedAt: '2026-09-25T08:21:07.390Z'
exploitAvailable: true
---

## Overview

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

xfs: resample the data fork mapping after cycling ILOCK

xfs_reflink_fill_{cow_hole,delalloc} are both presented with an inode,
a data fork mapping, and a cow fork mapping.  Unfortunately, these two
helpers cycle the ILOCK to grab a transaction, which means that the
mappings are stale as soon as we reacquire the ILOCK.  Currently we
refresh the cow fork mapping by re-calling xfs_find_trim_cow_extent, but
we don't refresh the data fork mapping beforehand, which means that the
xfs_bmap_trim_cow in that function queries the refcount btree about the
wrong physical blocks and returns an inaccurate value in *shared.

If *shared is now false, the directio write proceeds with a stale data
fork mapping.  Fix this by querying the data fork mapping if the
sequence counter changes across the ILOCK cycle.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.