CVE-2026-43103

Vulnerability

Overview The vulnerability exists in the Linux kernel's net/lapbether module. The function lapbeth_data_transmit() expects the underlying network device to be of type ARPHRD_ETHER. Without proper handling of the NETDEV_PRE_TYPE_CHANGE event, a bonding driver could alter the underlying device's type, breaking this assumption and leading to undefined behavior.

Exploitation

An attacker with the ability to create and manipulate a bonding interface could trigger a device type change while the lapbether driver is active. This does not require any special privileges beyond those needed to configure networking, but it does require the presence of a bonding device and the lapbether module.

Impact

If successfully exploited, the device type mismatch could cause kernel crashes, data corruption, or other unpredictable behavior. The fix ensures that the bonding driver is prevented from changing the device type by returning NOTIFY_BAD from lapbeth_device_event() when a NETDEV_PRE_TYPE_CHANGE notification occurs.

Mitigation

The fix has been applied in Linux kernel stable releases. Users are advised to update to the latest kernel version to mitigate the vulnerability. There are no known workarounds other than applying the kernel patch.