CVE-2025-39985: 
Linux Kernel vulnerability analysis and mitigation

A buffer overflow vulnerability (CVE-2025-39985) was discovered in the Linux kernel's mcbausb CAN driver, disclosed on October 15, 2025. The vulnerability affects the CAN framework logic and allows an attacker to bypass security checks through PFPACKET sockets (NVD).

The vulnerability stems from the mcbausb driver not populating its netdeviceops->ndochangemtu(), which allows an attacker to configure an invalid MTU. By setting an arbitrary MTU value (e.g., 'ip link set can0 mtu 9999') and using a PFPACKET socket with ETHPCANXL protocol, an attacker can inject malicious CAN XL frames. The driver misinterprets these frames as CAN frames, leading to a buffer overflow of up to 247 bytes when processing the frame's length field (NVD).

The vulnerability allows an attacker to cause a buffer overflow of up to 247 bytes, which could potentially lead to memory corruption and possible code execution in the kernel context. This poses a significant risk to system security and stability (NVD).

The vulnerability has been patched by populating the netdeviceops->ndochangemtu() function to ensure that the interface's MTU cannot be set to anything larger than CAN_MTU. This fix prevents the buffer overflow by addressing the root cause of the vulnerability (NVD).