---
id: CVE-2025-38708
title: 'drbd: add missing kref_get in handle_write_conflicts'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  drbd: add missing kref_get in handle_write_conflicts

  With `two-primaries` enabled, DRBD tries to detect "concurrent" writes
  and handle write conflicts, so that even if…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 <
    0336bfe9c237476bd7c45605a36ca79c2bca62e5
  - >-
    Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 <
    810cd546a29bfac90ed1328ea01d693d4bd11cb1
  - >-
    Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 <
    84ef8dd3238330d1795745ece83b19f0295751bf
  - >-
    Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 <
    57418de35420cedab035aa1da8a26c0499b7f575
  - >-
    Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 <
    9f53b2433ad248cd3342cc345f56f5c7904bd8c4
  - >-
    Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 <
    7d483ad300fc0a06f69b019dda8f74970714baf8
  - >-
    Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 <
    46e3763dcae0ffcf8fcfaff4fc10a90a92ffdd89
  - >-
    Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 <
    3a896498f6f577e57bf26aaa93b48c22b6d20c20
  - >-
    Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 <
    00c9c9628b49e368d140cfa61d7df9b8922ec2a8
  - Linux 4.5
published: '2025-09-04'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T01:07:44.390Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-38708'
references:
  - url: 'https://git.kernel.org/stable/c/0336bfe9c237476bd7c45605a36ca79c2bca62e5'
  - url: 'https://git.kernel.org/stable/c/810cd546a29bfac90ed1328ea01d693d4bd11cb1'
  - url: 'https://git.kernel.org/stable/c/84ef8dd3238330d1795745ece83b19f0295751bf'
  - url: 'https://git.kernel.org/stable/c/57418de35420cedab035aa1da8a26c0499b7f575'
  - url: 'https://git.kernel.org/stable/c/9f53b2433ad248cd3342cc345f56f5c7904bd8c4'
  - url: 'https://git.kernel.org/stable/c/7d483ad300fc0a06f69b019dda8f74970714baf8'
  - url: 'https://git.kernel.org/stable/c/46e3763dcae0ffcf8fcfaff4fc10a90a92ffdd89'
  - url: 'https://git.kernel.org/stable/c/3a896498f6f577e57bf26aaa93b48c22b6d20c20'
  - url: 'https://git.kernel.org/stable/c/00c9c9628b49e368d140cfa61d7df9b8922ec2a8'
tags:
  - cve.org
epss: 0.00379
epssPercentile: 0.31727
ingestedAt: '2026-10-15T05:52:46.082Z'
---

## Overview

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

drbd: add missing kref_get in handle_write_conflicts

With `two-primaries` enabled, DRBD tries to detect "concurrent" writes
and handle write conflicts, so that even if you write to the same sector
simultaneously on both nodes, they end up with the identical data once
the writes are completed.

In handling "superseeded" writes, we forgot a kref_get,
resulting in a premature drbd_destroy_device and use after free,
and further to kernel crashes with symptoms.

Relevance: No one should use DRBD as a random data generator, and apparently
all users of "two-primaries" handle concurrent writes correctly on layer up.
That is cluster file systems use some distributed lock manager,
and live migration in virtualization environments stops writes on one node
before starting writes on the other node.

Which means that other than for "test cases",
this code path is never taken in real life.

FYI, in DRBD 9, things are handled differently nowadays.  We still detect
"write conflicts", but no longer try to be smart about them.
We decided to disconnect hard instead: upper layers must not submit concurrent
writes. If they do, that's their fault.

## Affected

- `Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 < 0336bfe9c237476bd7c45605a36ca79c2bca62e5`
- `Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 < 810cd546a29bfac90ed1328ea01d693d4bd11cb1`
- `Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 < 84ef8dd3238330d1795745ece83b19f0295751bf`
- `Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 < 57418de35420cedab035aa1da8a26c0499b7f575`
- `Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 < 9f53b2433ad248cd3342cc345f56f5c7904bd8c4`
- `Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 < 7d483ad300fc0a06f69b019dda8f74970714baf8`
- `Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 < 46e3763dcae0ffcf8fcfaff4fc10a90a92ffdd89`
- `Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 < 3a896498f6f577e57bf26aaa93b48c22b6d20c20`
- `Linux >= 668700b40a7c8727bbd2b3fd4fd22e0ce3f1aeb6 < 00c9c9628b49e368d140cfa61d7df9b8922ec2a8`
- `Linux 4.5`

## Remediation

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