CVE-2025-39987
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
In the Linux kernel's hi311x CAN driver, the missing ndo_change_mtu() implementation allows an attacker to set an invalid MTU (e.g., 9999) and send a malicious CAN XL frame via a PF_PACKET socket. This causes a buffer overflow in hi3110_hw_tx() when copying frame data, as the driver misinterprets the CAN XL frame as a regular CAN frame.
Risk Assessment
An attacker can remotely trigger a buffer overflow in the driver, leading to potential arbitrary code execution in kernel context or system crash (DoS). This vulnerability enables privilege escalation or destabilization of critical systems using CAN interfaces.
Recommendation
Immediately update the Linux kernel to a version containing the fix that adds ndo_change_mtu() to limit MTU to CAN_MTU. If updating is not possible, restrict access to CAN interfaces to trusted users only.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: can: hi311x: populate ndo_change_mtu() to prevent buffer overflow Sending an PF_PACKET 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 PF_PACKET framework is to make sure that skb->len fits the interface's MTU. Unfortunately, because the sun4i_can driver does not populate its net_device_ops->ndo_change_mtu(), 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 PF_PACKET socket using the ETH_P_CANXL protocol: socket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL)) to inject a malicious CAN XL frames. For example: struct canxl_frame frame = { .flags = 0xff, .len = 2048, }; The CAN drivers' xmit() function are calling can_dev_dropped_skb() to check that the skb is valid, unfortunately under above conditions, the malicious packet is able to go through can_dev_dropped_skb() checks: 1. the skb->protocol is set to ETH_P_CANXL which is valid (the function does not check the actual device capabilities). 2. the length is a valid CAN XL length. And so, hi3110_hard_start_xmit() receives a CAN XL frame which it is not able to correctly handle and will thus misinterpret it as a CAN frame. The driver will consume frame->len as-is with no further checks. This can result in a buffer overflow later on in hi3110_hw_tx() on this line: memcpy(buf + HI3110_FIFO_EXT_DATA_OFF, frame->data, frame->len); Here, frame->len corresponds to the flags field of the CAN XL frame. In our previous example, we set canxl_frame->flags to 0xff. Because the maximum expected length is 8, a buffer overflow of 247 bytes occurs! Populate net_device_ops->ndo_change_mtu() to ensure that the interface's MTU can not be set to anything bigger than CAN_MTU. By fixing the root cause, this prevents the buffer overflow.