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  - can: sun4i_can: 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, sun4ican_start_xmit() 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 this line: dlc = cf->len; Here, cf->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 a couple line below when doing: for (i     = 0; i < dlc; i++) writel(cf->data[i], priv->base + (dreg + i * 4)); 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. (CVE-2025-39986)

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Linux Distros Unpatched Vulnerability : CVE-2025-39986

high Nessus Plugin ID 271541

Version 1.3