---
id: CVE-2026-68442
title: 'btrfs: don''t propagate EXTENT_FLAG_LOGGING to split extent maps'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  btrfs: don't propagate EXTENT_FLAG_LOGGING to split extent maps

  When btrfs_drop_extent_map_range() splits an extent map, the new split
  maps inherit the original map's …
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'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9 <
    2a9246a424f45f33a1b8367052611ebe874868ad
  - >-
    Linux >= f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9 <
    9304713b70e7e1450e3a76e758836fe5391bfa95
  - >-
    Linux >= f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9 <
    0e465c63f103a5ce6849614d6bda048d70eebec8
  - >-
    Linux >= f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9 <
    5eff4d5b17fa1950e80bfd1ba43dc0699e61a644
  - Linux 6.8
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T15:48:58.466646Z'
published: '2026-08-12'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:53:13.663Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-68442'
references:
  - url: 'https://git.kernel.org/stable/c/2a9246a424f45f33a1b8367052611ebe874868ad'
  - url: 'https://git.kernel.org/stable/c/9304713b70e7e1450e3a76e758836fe5391bfa95'
  - url: 'https://git.kernel.org/stable/c/0e465c63f103a5ce6849614d6bda048d70eebec8'
  - url: 'https://git.kernel.org/stable/c/5eff4d5b17fa1950e80bfd1ba43dc0699e61a644'
tags:
  - cve.org
epss: 0.00117
epssPercentile: 0.01543
ingestedAt: '2026-10-16T17:24:46.868Z'
---

## Overview

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

btrfs: don't propagate EXTENT_FLAG_LOGGING to split extent maps

When btrfs_drop_extent_map_range() splits an extent map, the new split
maps inherit the original map's flags through a local 'flags' variable.
Commit f86f7a75e2fb ("btrfs: use the flags of an extent map to identify
the compression type") changed the EXTENT_FLAG_LOGGING clearing to
operate on em->flags instead of that local 'flags' copy, so a split of
an extent map that is currently being logged wrongly inherits
EXTENT_FLAG_LOGGING.

The flag is then never cleared on the split, and when it is freed while
still on the inode's modified_extents list (for example by the extent
map shrinker) it trips the WARN_ON(!list_empty(&em->list)) in
btrfs_free_extent_map() and leads to a use-after-free.

Clear EXTENT_FLAG_LOGGING from the local 'flags' copy used for the
splits and only clear EXTENT_FLAG_PINNED from em->flags, restoring the
behaviour prior to f86f7a75e2fb.

## Affected

- `Linux >= f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9 < 2a9246a424f45f33a1b8367052611ebe874868ad`
- `Linux >= f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9 < 9304713b70e7e1450e3a76e758836fe5391bfa95`
- `Linux >= f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9 < 0e465c63f103a5ce6849614d6bda048d70eebec8`
- `Linux >= f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9 < 5eff4d5b17fa1950e80bfd1ba43dc0699e61a644`
- `Linux 6.8`

## Remediation

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