Skip to main content
VulnerabilityPublished Updated

CVE-2026-63990: Linux kernel · bonding: refuse to enslave CAN devices

Affects Linux kernelSource GCVE Database

0

Not known to be exploited · CVSS 5.5 Medium · fixed in 5.15.0-1117.124~20.04.1 : update Linux kernel when convenient.

Data as of 28 Oct 2026, 11:45 UTC

CVSS 3.1 base score
5.5Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +67
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-28.28
Fixed in
  • 7.0.0-28.28
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-1009.9
Fixed in
  • 7.0.0-1009.9
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-1010.10
Fixed in
  • 7.0.0-1010.10
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-1009.9
Fixed in
  • 7.0.0-1009.9
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-1008.8
Fixed in
  • 7.0.0-1008.8
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threatsAffected
  • <7.0.0-1003.4
Fixed in
  • 7.0.0-1003.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

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.

References

Community reviews

Loading reviews…