---
id: CVE-2026-31666
title: >-
  btrfs: fix incorrect return value after changing leaf in
  lookup_extent_data_ref()
summary: >-
  In the Linux kernel, the following vulnerability has been resolved:


  btrfs: fix incorrect return value after changing leaf in
  lookup_extent_data_ref()


  After commit 1618aa3c2e01 ("btrfs: simplify return variables in

  lookup_extent_data_re…
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 >= 1618aa3c2e0163f5ac34d514ae89474521910536 <
    4125a194db4a6cf91f619f38788272651cb97dce
  - >-
    Linux >= 1618aa3c2e0163f5ac34d514ae89474521910536 <
    450e6a685d0cad95b15f8af152057bd0bf79f50b
  - >-
    Linux >= 1618aa3c2e0163f5ac34d514ae89474521910536 <
    ab1e022379c3c811aa72da8eb0c7507859a1d0f5
  - >-
    Linux >= 1618aa3c2e0163f5ac34d514ae89474521910536 <
    316fb1b3169efb081d2db910cbbfef445afa03b9
  - Linux 6.10
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T15:11:52.641665Z'
published: '2026-04-24'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:20:21.898Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31666'
references:
  - url: 'https://git.kernel.org/stable/c/4125a194db4a6cf91f619f38788272651cb97dce'
  - url: 'https://git.kernel.org/stable/c/450e6a685d0cad95b15f8af152057bd0bf79f50b'
  - url: 'https://git.kernel.org/stable/c/ab1e022379c3c811aa72da8eb0c7507859a1d0f5'
  - url: 'https://git.kernel.org/stable/c/316fb1b3169efb081d2db910cbbfef445afa03b9'
tags:
  - cve.org
epss: 0.00175
epssPercentile: 0.06541
ingestedAt: '2026-10-16T17:24:46.668Z'
---

## Overview

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

btrfs: fix incorrect return value after changing leaf in lookup_extent_data_ref()

After commit 1618aa3c2e01 ("btrfs: simplify return variables in
lookup_extent_data_ref()"), the err and ret variables were merged into
a single ret variable. However, when btrfs_next_leaf() returns 0
(success), ret is overwritten from -ENOENT to 0. If the first key in
the next leaf does not match (different objectid or type), the function
returns 0 instead of -ENOENT, making the caller believe the lookup
succeeded when it did not. This can lead to operations on the wrong
extent tree item, potentially causing extent tree corruption.

Fix this by returning -ENOENT directly when the key does not match,
instead of relying on the ret variable.

## Affected

- `Linux >= 1618aa3c2e0163f5ac34d514ae89474521910536 < 4125a194db4a6cf91f619f38788272651cb97dce`
- `Linux >= 1618aa3c2e0163f5ac34d514ae89474521910536 < 450e6a685d0cad95b15f8af152057bd0bf79f50b`
- `Linux >= 1618aa3c2e0163f5ac34d514ae89474521910536 < ab1e022379c3c811aa72da8eb0c7507859a1d0f5`
- `Linux >= 1618aa3c2e0163f5ac34d514ae89474521910536 < 316fb1b3169efb081d2db910cbbfef445afa03b9`
- `Linux 6.10`

## Remediation

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