---
id: CVE-2026-43249
title: '9p/xen: protect xen_9pfs_front_free against concurrent calls'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  9p/xen: protect xen_9pfs_front_free against concurrent calls

  The xenwatch thread can race with other back-end change notifications
  and call xen_9pfs_front_free() twice…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= c15fe55d14b3b4ded5af2a3260877460a6ffb8ad <
    480aa6ffd4ac7036eea042047d0cca71bc2074bb
  - >-
    Linux >= c15fe55d14b3b4ded5af2a3260877460a6ffb8ad <
    a5d00dff97118a32fcf5fec7a4c3f864c4620c4e
  - >-
    Linux >= c15fe55d14b3b4ded5af2a3260877460a6ffb8ad <
    59e7707492576bdbfa8c1dbe7d90791df31e4773
  - >-
    Linux >= c15fe55d14b3b4ded5af2a3260877460a6ffb8ad <
    bf841d43f7a33d75675ba7f4e214ac1c67913065
  - >-
    Linux >= c15fe55d14b3b4ded5af2a3260877460a6ffb8ad <
    ce8ded2e61f47747e31eeefb44dc24a2160a7e32
  - Linux be03c4fe72384366fd4077a70966bd3b8fc49013
  - Linux 1ab4de11232e83b875b071aa44d1155634ca8a1e
  - Linux 7cc9dbae8a5f73bd555130384ea256018d28f283
  - Linux 3e0359f151ac151abe3fa71040e450ed69cb824b
  - Linux 8d3fc907d060c4fb33203e616a395a22083b6566
  - Linux 4f0e9244770f5b75a16d8c0929063cd336926764
  - Linux 5f6a8974e9ef317fe63f88bab1f33070195dd147
  - Linux >= 4.14.308 < 4.15
  - Linux >= 4.19.276 < 4.20
  - Linux >= 5.4.235 < 5.5
  - Linux >= 5.10.173 < 5.11
  - Linux >= 5.15.100 < 5.16
  - Linux >= 6.1.18 < 6.2
  - Linux >= 6.2.5 < 6.3
  - Linux 6.3
published: '2026-05-06'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T12:40:24.296Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-43249'
references:
  - url: 'https://git.kernel.org/stable/c/480aa6ffd4ac7036eea042047d0cca71bc2074bb'
  - url: 'https://git.kernel.org/stable/c/a5d00dff97118a32fcf5fec7a4c3f864c4620c4e'
  - url: 'https://git.kernel.org/stable/c/59e7707492576bdbfa8c1dbe7d90791df31e4773'
  - url: 'https://git.kernel.org/stable/c/bf841d43f7a33d75675ba7f4e214ac1c67913065'
  - url: 'https://git.kernel.org/stable/c/ce8ded2e61f47747e31eeefb44dc24a2160a7e32'
tags:
  - cve.org
epss: 0.00379
epssPercentile: 0.3047
ingestedAt: '2026-10-21T12:48:53.645Z'
---

## Overview

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

9p/xen: protect xen_9pfs_front_free against concurrent calls

The xenwatch thread can race with other back-end change notifications
and call xen_9pfs_front_free() twice, hitting the observed general
protection fault due to a double-free. Guard the teardown path so only
one caller can release the front-end state at a time, preventing the
crash.

This is a fix for the following double-free:

[   27.052347] Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b6b: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI
[   27.052357] CPU: 0 UID: 0 PID: 32 Comm: xenwatch Not tainted 6.18.0-02087-g51ab33fc0a8b-dirty #60 PREEMPT(none)
[   27.052363] RIP: e030:xen_9pfs_front_free+0x1d/0x150
[   27.052368] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 41 55 41 54 55 48 89 fd 48 c7 c7 48 d0 92 85 53 e8 cb cb 05 00 48 8b 45 08 48 8b 55 00 <48> 3b 28 0f 85 f9 28 35 fe 48 3b 6a 08 0f 85 ef 28 35 fe 48 89 42
[   27.052377] RSP: e02b:ffffc9004016fdd0 EFLAGS: 00010246
[   27.052381] RAX: 6b6b6b6b6b6b6b6b RBX: ffff88800d66e400 RCX: 0000000000000000
[   27.052385] RDX: 6b6b6b6b6b6b6b6b RSI: 0000000000000000 RDI: 0000000000000000
[   27.052389] RBP: ffff88800a887040 R08: 0000000000000000 R09: 0000000000000000
[   27.052393] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888009e46b68
[   27.052397] R13: 0000000000000200 R14: 0000000000000000 R15: ffff88800a887040
[   27.052404] FS:  0000000000000000(0000) GS:ffff88808ca57000(0000) knlGS:0000000000000000
[   27.052408] CS:  e030 DS: 0000 ES: 0000 CR0: 0000000080050033
[   27.052412] CR2: 00007f9714004360 CR3: 0000000004834000 CR4: 0000000000050660
[   27.052418] Call Trace:
[   27.052420]  <TASK>
[   27.052422]  xen_9pfs_front_changed+0x5d5/0x720
[   27.052426]  ? xenbus_otherend_changed+0x72/0x140
[   27.052430]  ? __pfx_xenwatch_thread+0x10/0x10
[   27.052434]  xenwatch_thread+0x94/0x1c0
[   27.052438]  ? __pfx_autoremove_wake_function+0x10/0x10
[   27.052442]  kthread+0xf8/0x240
[   27.052445]  ? __pfx_kthread+0x10/0x10
[   27.052449]  ? __pfx_kthread+0x10/0x10
[   27.052452]  ret_from_fork+0x16b/0x1a0
[   27.052456]  ? __pfx_kthread+0x10/0x10
[   27.052459]  ret_from_fork_asm+0x1a/0x30
[   27.052463]  </TASK>
[   27.052465] Modules linked in:
[   27.052471] ---[ end trace 0000000000000000 ]---

## Affected

- `Linux >= c15fe55d14b3b4ded5af2a3260877460a6ffb8ad < 480aa6ffd4ac7036eea042047d0cca71bc2074bb`
- `Linux >= c15fe55d14b3b4ded5af2a3260877460a6ffb8ad < a5d00dff97118a32fcf5fec7a4c3f864c4620c4e`
- `Linux >= c15fe55d14b3b4ded5af2a3260877460a6ffb8ad < 59e7707492576bdbfa8c1dbe7d90791df31e4773`
- `Linux >= c15fe55d14b3b4ded5af2a3260877460a6ffb8ad < bf841d43f7a33d75675ba7f4e214ac1c67913065`
- `Linux >= c15fe55d14b3b4ded5af2a3260877460a6ffb8ad < ce8ded2e61f47747e31eeefb44dc24a2160a7e32`
- `Linux be03c4fe72384366fd4077a70966bd3b8fc49013`
- `Linux 1ab4de11232e83b875b071aa44d1155634ca8a1e`
- `Linux 7cc9dbae8a5f73bd555130384ea256018d28f283`
- `Linux 3e0359f151ac151abe3fa71040e450ed69cb824b`
- `Linux 8d3fc907d060c4fb33203e616a395a22083b6566`
- `Linux 4f0e9244770f5b75a16d8c0929063cd336926764`
- `Linux 5f6a8974e9ef317fe63f88bab1f33070195dd147`
- `Linux >= 4.14.308 < 4.15`
- `Linux >= 4.19.276 < 4.20`
- `Linux >= 5.4.235 < 5.5`
- `Linux >= 5.10.173 < 5.11`
- `Linux >= 5.15.100 < 5.16`
- `Linux >= 6.1.18 < 6.2`
- `Linux >= 6.2.5 < 6.3`
- `Linux 6.3`

## Remediation

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