---
id: CVE-2026-23209
title: 'macvlan: fix error recovery in macvlan_common_newlink()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  macvlan: fix error recovery in macvlan_common_newlink()

  valis provided a nice repro to crash the kernel:

  ip link add p1 type veth peer p2
  ip link set address 00:00:00…
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 >= aa5fd0fb77486b8a6764ead8627baa14790e4280 <
    da5c6b8ae47e414be47e5e04def15b25d5c962dc
  - >-
    Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 <
    5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a
  - >-
    Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 <
    c43d0e787cbba569ec9d11579ed370b50fab6c9c
  - >-
    Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 <
    11ba9f0dc865136174cb98834280fb21bbc950c7
  - >-
    Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 <
    986967a162142710076782d5b93daab93a892980
  - >-
    Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 <
    cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66
  - >-
    Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 <
    f8db6475a83649689c087a8f52486fcc53e627e9
  - Linux 4.9
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-06-16T20:31:00.910619Z'
published: '2026-02-14'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T18:35:38.702Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-23209'
references:
  - url: 'https://git.kernel.org/stable/c/da5c6b8ae47e414be47e5e04def15b25d5c962dc'
  - url: 'https://git.kernel.org/stable/c/5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a'
  - url: 'https://git.kernel.org/stable/c/c43d0e787cbba569ec9d11579ed370b50fab6c9c'
  - url: 'https://git.kernel.org/stable/c/11ba9f0dc865136174cb98834280fb21bbc950c7'
  - url: 'https://git.kernel.org/stable/c/986967a162142710076782d5b93daab93a892980'
  - url: 'https://git.kernel.org/stable/c/cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66'
  - url: 'https://git.kernel.org/stable/c/f8db6475a83649689c087a8f52486fcc53e627e9'
tags:
  - cve.org
epss: 0.0014
epssPercentile: 0.02994
ingestedAt: '2026-10-19T19:38:06.501Z'
---

## Overview

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

macvlan: fix error recovery in macvlan_common_newlink()

valis provided a nice repro to crash the kernel:

ip link add p1 type veth peer p2
ip link set address 00:00:00:00:00:20 dev p1
ip link set up dev p1
ip link set up dev p2

ip link add mv0 link p2 type macvlan mode source
ip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20

ping -c1 -I p1 1.2.3.4

He also gave a very detailed analysis:

<quote valis>

The issue is triggered when a new macvlan link is created  with
MACVLAN_MODE_SOURCE mode and MACVLAN_MACADDR_ADD (or
MACVLAN_MACADDR_SET) parameter, lower device already has a macvlan
port and register_netdevice() called from macvlan_common_newlink()
fails (e.g. because of the invalid link name).

In this case macvlan_hash_add_source is called from
macvlan_change_sources() / macvlan_common_newlink():

This adds a reference to vlan to the port's vlan_source_hash using
macvlan_source_entry.

vlan is a pointer to the priv data of the link that is being created.

When register_netdevice() fails, the error is returned from
macvlan_newlink() to rtnl_newlink_create():

        if (ops->newlink)
                err = ops->newlink(dev, &params, extack);
        else
                err = register_netdevice(dev);
        if (err < 0) {
                free_netdev(dev);
                goto out;
        }

and free_netdev() is called, causing a kvfree() on the struct
net_device that is still referenced in the source entry attached to
the lower device's macvlan port.

Now all packets sent on the macvlan port with a matching source mac
address will trigger a use-after-free in macvlan_forward_source().

</quote valis>

With all that, my fix is to make sure we call macvlan_flush_sources()
regardless of @create value whenever "goto destroy_macvlan_port;"
path is taken.

Many thanks to valis for following up on this issue.

## Affected

- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < da5c6b8ae47e414be47e5e04def15b25d5c962dc`
- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < 5dae6b36a7cb7a4fcf4121b95e9ca7f96f816c8a`
- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < c43d0e787cbba569ec9d11579ed370b50fab6c9c`
- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < 11ba9f0dc865136174cb98834280fb21bbc950c7`
- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < 986967a162142710076782d5b93daab93a892980`
- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < cdedcd5aa3f3cb8b7ae0f87ab3a936d0bd583d66`
- `Linux >= aa5fd0fb77486b8a6764ead8627baa14790e4280 < f8db6475a83649689c087a8f52486fcc53e627e9`
- `Linux 4.9`

## Remediation

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