---
id: CVE-2021-47082
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  tun: avoid double free in tun_free_netdev

  Avoid double free in tun_free_netdev() by moving the
  dev->tstats and tun->security allocs to a new ndo_init routine
  (tun_net_…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  tun: avoid double free in tun_free_netdev

  Avoid double free in tun_free_netdev() by moving the
  dev->tstats and tun->security allocs to a new ndo_init routine
  (tun_net_…
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'
cwe:
  - CWE-415
vendor: linux
product: linux_kernel
affected:
  - linux_kernel < 4.19.280
  - 'linux_kernel >= 4.20, < 5.4.240'
  - 'linux_kernel >= 5.5, < 5.10.136'
  - 'linux_kernel >= 5.11, < 5.15.12'
  - linux_kernel = 5.16
patched:
  - linux_kernel 5.15.12
published: '2024-03-04'
updated: '2026-08-04'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2021-47082'
references:
  - url: 'https://git.kernel.org/stable/c/0c0e566f0387490d16f166808c72e9c772027681'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/158b515f703e75e7d68289bf4d98c664e1d632df'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3cb5ae77799e8ed6ec3fec0b6b4cd07f01650cc5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8eb43d635950e27c29f1e9e49a23b31637f37757'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a01a4e9f5dc93335c716fa4023b1901956e8c904'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/0c0e566f0387490d16f166808c72e9c772027681'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/158b515f703e75e7d68289bf4d98c664e1d632df'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/3cb5ae77799e8ed6ec3fec0b6b4cd07f01650cc5'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/8eb43d635950e27c29f1e9e49a23b31637f37757'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://git.kernel.org/stable/c/a01a4e9f5dc93335c716fa4023b1901956e8c904'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.00252
epssPercentile: 0.14867
ingestedAt: '2026-08-05T05:58:02.375Z'
---

## Overview

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

tun: avoid double free in tun_free_netdev

Avoid double free in tun_free_netdev() by moving the
dev->tstats and tun->security allocs to a new ndo_init routine
(tun_net_init()) that will be called by register_netdevice().
ndo_init is paired with the desctructor (tun_free_netdev()),
so if there's an error in register_netdevice() the destructor
will handle the frees.

BUG: KASAN: double-free or invalid-free in selinux_tun_dev_free_security+0x1a/0x20 security/selinux/hooks.c:5605

CPU: 0 PID: 25750 Comm: syz-executor416 Not tainted 5.16.0-rc2-syzk #1
Hardware name: Red Hat KVM, BIOS
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106
print_address_description.constprop.9+0x28/0x160 mm/kasan/report.c:247
kasan_report_invalid_free+0x55/0x80 mm/kasan/report.c:372
____kasan_slab_free mm/kasan/common.c:346 [inline]
__kasan_slab_free+0x107/0x120 mm/kasan/common.c:374
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:1723 [inline]
slab_free_freelist_hook mm/slub.c:1749 [inline]
slab_free mm/slub.c:3513 [inline]
kfree+0xac/0x2d0 mm/slub.c:4561
selinux_tun_dev_free_security+0x1a/0x20 security/selinux/hooks.c:5605
security_tun_dev_free_security+0x4f/0x90 security/security.c:2342
tun_free_netdev+0xe6/0x150 drivers/net/tun.c:2215
netdev_run_todo+0x4df/0x840 net/core/dev.c:10627
rtnl_unlock+0x13/0x20 net/core/rtnetlink.c:112
__tun_chr_ioctl+0x80c/0x2870 drivers/net/tun.c:3302
tun_chr_ioctl+0x2f/0x40 drivers/net/tun.c:3311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__x64_sys_ioctl+0x19d/0x220 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

## Affected

- `linux_kernel < 4.19.280`
- `linux_kernel >= 4.20, < 5.4.240`
- `linux_kernel >= 5.5, < 5.10.136`
- `linux_kernel >= 5.11, < 5.15.12`
- `linux_kernel = 5.16`

## Remediation

Upgrade past the affected range:

- `linux_kernel 5.15.12`