---
id: CVE-2026-63990
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bonding: refuse to enslave CAN devices

  syzbot reported a kernel paging request crash in
  can_rx_unregister() inside net/can/af_can.c
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  bonding: refuse to enslave CAN devices

  syzbot reported a kernel paging request crash in
  can_rx_unregister() inside net/can/af_can.c. The crash occurs
  because a virtual…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-401
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.25, < 5.15.210'
  - 'linux_kernel >= 5.16, < 6.1.176'
  - 'linux_kernel >= 6.2, < 6.6.143'
  - 'linux_kernel >= 6.7, < 6.12.93'
  - 'linux_kernel >= 6.13, < 6.18.35'
  - 'linux_kernel >= 6.19, < 7.0.12'
  - linux_kernel = 7.1
patched:
  - linux_kernel 7.0.12
published: '2026-07-19'
updated: '2026-10-07'
sourceUpdated: '2026-10-07T20:31:37.400'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63990'
references:
  - url: 'https://git.kernel.org/stable/c/02f1c87ded33b43d48b4a1d665da15f2157b30d8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/41e8478c4cd896d3abbe33d41afc90c84ac66602'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/563090e5d450c665f70d955a39f9587afc7842eb'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/69b78b5f3033272e53a2dc2dad675962654a5b38'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/8ba68464e4787b6a7ec938826e16124df20fd23d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9ea8a648d9120f7652bcde1ce2c4ad66871af707'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/f4d78a81f57df82e9d82a2c07471fed1a1235893'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00181
epssPercentile: 0.07017
ingestedAt: '2026-10-07T20:46:46.957Z'
---

## Overview

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

bonding: refuse to enslave CAN devices

syzbot reported a kernel paging request crash in
can_rx_unregister() inside net/can/af_can.c. The crash occurs
because a virtual CAN device (vxcan) is being enslaved to a
bonding master.

During the enslavement process, the bonding driver mutates
and modifies the network device states to fit an Ethernet-like
aggregation model. However, CAN devices operate on a completely
different Layer 2 architecture, relying on the CAN mid-layer
private data structure (can_ml_priv) instead of standard
Ethernet structures. Since bonding does not initialize or
maintain these CAN structures, subsequent operations on the
half-enslaved interface (such as closing associated sockets
via isotp_release) lead to a null-pointer dereference when
accessing the CAN receiver lists.

Bonding CAN interfaces is architecturally invalid as CAN lacks
MAC addresses, ARP capabilities, and standard Ethernet
link-layer mechanisms. While generic loopback devices are
blocked globally in net/core/dev.c, virtual CAN devices
bypass this check because they do not carry the IFF_LOOPBACK
flag, despite acting as local software-loopbacks.

Fix this by explicitly blocking network devices of type
ARPHRD_CAN from being enslaved at the very beginning of
bond_enslave(). This prevents illegal state mutations,
eliminates the resulting KASAN crashes, and avoids potential
memory leaks from incomplete socket cleanups.

As the CAN support has been added a long time after bonding
the Fixes-tag points to the introduction of ARPHRD_CAN that
would have needed a specific handling in bonding_main.c.

## Affected

- `linux_kernel >= 2.6.25, < 5.15.210`
- `linux_kernel >= 5.16, < 6.1.176`
- `linux_kernel >= 6.2, < 6.6.143`
- `linux_kernel >= 6.7, < 6.12.93`
- `linux_kernel >= 6.13, < 6.18.35`
- `linux_kernel >= 6.19, < 7.0.12`
- `linux_kernel = 7.1`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.0.12`