In the Linux kernel, the following vulnerability has been resolved: can: mcbausb: populate ndochangemtu() to prevent buffer overflow Sending an PFPACKET allows to bypass the CAN framework logic and to directly reach the xmit() function of a CAN driver. The only check which is performed by the PFPACKET framework is to make sure that skb->len fits the interface's MTU. Unfortunately, because the mcbausb driver does not populate its netdeviceops->ndochangemtu(), it is possible for an attacker to configure an invalid MTU by doing, for example: $ ip link set can0 mtu 9999 After doing so, the attacker could open a PFPACKET socket using the ETHPCANXL protocol: socket(PFPACKET, SOCKRAW, htons(ETHPCANXL)) to inject a malicious CAN XL frames. For example: struct canxlframe frame = { .flags = 0xff, .len = 2048, }; The CAN drivers' xmit() function are calling candevdroppedskb() to check that the skb is valid, unfortunately under above conditions, the malicious packet is able to go through candevdroppedskb() checks: 1. the skb->protocol is set to ETHPCANXL which is valid (the function does not check the actual device capabilities). 2. the length is a valid CAN XL length. And so, mcbausbstartxmit() receives a CAN XL frame which it is not able to correctly handle and will thus misinterpret it as a CAN frame. This can result in a buffer overflow. The driver will consume cf->len as-is with no further checks on these lines: usbmsg.dlc = cf->len; memcpy(usbmsg.data, cf->data, usbmsg.dlc); Here, cf->len corresponds to the flags field of the CAN XL frame. In our previous example, we set canxlframe->flags to 0xff. Because the maximum expected length is 8, a buffer overflow of 247 bytes occurs! Populate netdeviceops->ndochangemtu() to ensure that the interface's MTU can not be set to anything bigger than CANMTU. By fixing the root cause, this prevents the buffer overflow.