{"id":"AZL-68516","summary":"CVE-2025-39987 affecting package kernel for versions less than 6.6.112.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ncan: hi311x: populate ndo_change_mtu() to prevent buffer overflow\n\nSending an PF_PACKET allows to bypass the CAN framework logic and to\ndirectly reach the xmit() function of a CAN driver. The only check\nwhich is performed by the PF_PACKET framework is to make sure that\nskb-\u003elen fits the interface's MTU.\n\nUnfortunately, because the sun4i_can driver does not populate its\nnet_device_ops-\u003endo_change_mtu(), it is possible for an attacker to\nconfigure an invalid MTU by doing, for example:\n\n  $ ip link set can0 mtu 9999\n\nAfter doing so, the attacker could open a PF_PACKET socket using the\nETH_P_CANXL protocol:\n\n\tsocket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL))\n\nto inject a malicious CAN XL frames. For example:\n\n\tstruct canxl_frame frame = {\n\t\t.flags = 0xff,\n\t\t.len = 2048,\n\t};\n\nThe CAN drivers' xmit() function are calling can_dev_dropped_skb() to\ncheck that the skb is valid, unfortunately under above conditions, the\nmalicious packet is able to go through can_dev_dropped_skb() checks:\n\n  1. the skb-\u003eprotocol is set to ETH_P_CANXL which is valid (the\n     function does not check the actual device capabilities).\n\n  2. the length is a valid CAN XL length.\n\nAnd so, hi3110_hard_start_xmit() receives a CAN XL frame which it is\nnot able to correctly handle and will thus misinterpret it as a CAN\nframe. The driver will consume frame-\u003elen as-is with no further\nchecks.\n\nThis can result in a buffer overflow later on in hi3110_hw_tx() on\nthis line:\n\n\tmemcpy(buf + HI3110_FIFO_EXT_DATA_OFF,\n\t       frame-\u003edata, frame-\u003elen);\n\nHere, frame-\u003elen corresponds to the flags field of the CAN XL frame.\nIn our previous example, we set canxl_frame-\u003eflags to 0xff. Because\nthe maximum expected length is 8, a buffer overflow of 247 bytes\noccurs!\n\nPopulate net_device_ops-\u003endo_change_mtu() to ensure that the\ninterface's MTU can not be set to anything bigger than CAN_MTU. By\nfixing the root cause, this prevents the buffer overflow.","modified":"2026-04-01T05:21:26.821731Z","published":"2025-10-15T08:15:36Z","upstream":["CVE-2025-39987"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39987"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.112.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-68516.json"}}],"schema_version":"1.7.5"}