CVE-2026-43012

The vulnerability arises when the Linux kernel attempts to roll back from switchdev mode to legacy mode due to a failure. During this rollback, an unregistration of the uplink network device occurs, leaving the device in an unregistered state. This triggers a kernel BUG at dev.c, resulting in a kernel panic and loss of service. The fault does not provide an attacker with a direct code execution or privilege escalation path; the impact is primarily failure of the network stack and the entire system. The weakness falls under improper resource cleanup in kernel code.

All Linux kernel distributions that include the mlx5 network driver and support the eswitch devlink interface are potentially affected. The issue may manifest when the operating system runs drivers that provide switchdev or eswitch functionality for Mellanox NICs. Affected kernels are those prior to the commit that added the rollback flag 'MLX5_PRIV_FLAGS_SWITCH_LEGACY', typically before kernel 6.17. No specific vendor or product release numbers are listed, so any kernel build the standard Linux source that includes the mlx5 driver and switchdev code is in scope.

The CVSS score is 5.5 and EPSS score is 0.00023 (< 1%), so the quantified risk measure indicates moderate severity. The bug causes a kernel panic, a denial‑of‑service condition that can be triggered by administrative devlink or network configuration commands that attempt to enable or disable eswitch mode. Because the exploit requires knowledge of the device and initiates a kernel‑level command, it is likely limited to a local or privileged user. Nevertheless, the potential for service interruption warrants immediate patching. The vulnerability is not listed in the CISA KEV catalog, implying there is no publicly known exploit at the time of release. Because the failure occurs during a controlled rollback, a legitimate system administration action could inadvertently trigger it, so the risk is operationally significant for users of Mellanox switches with switchdev support.