{"id":"CVE-2025-39985","summary":"can: mcba_usb: populate ndo_change_mtu() to prevent buffer overflow","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ncan: mcba_usb: 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 mcba_usb 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, mcba_usb_start_xmit() receives a CAN XL frame which it is not\nable to correctly handle and will thus misinterpret it as a CAN frame.\n\nThis can result in a buffer overflow. The driver will consume cf-\u003elen\nas-is with no further checks on these lines:\n\n\tusb_msg.dlc = cf-\u003elen;\n\n\tmemcpy(usb_msg.data, cf-\u003edata, usb_msg.dlc);\n\nHere, cf-\u003elen corresponds to the flags field of the CAN XL frame. In\nour previous example, we set canxl_frame-\u003eflags to 0xff. Because the\nmaximum expected length is 8, a buffer overflow of 247 bytes occurs!\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":"2026-04-02T12:48:14.497214Z","published":"2025-10-15T07:56:04.439Z","related":["MGASA-2025-0309","MGASA-2025-0310","SUSE-SU-2025:21040-1","SUSE-SU-2025:21052-1","SUSE-SU-2025:21056-1","SUSE-SU-2025:21064-1","SUSE-SU-2025:21080-1","SUSE-SU-2025:21147-1","SUSE-SU-2025:21180-1","SUSE-SU-2025:4057-1","SUSE-SU-2025:4128-1","SUSE-SU-2025:4132-1","SUSE-SU-2025:4140-1","SUSE-SU-2025:4141-1","SUSE-SU-2025:4301-1","openSUSE-SU-2025:20091-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39985.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0fa9303c4b9493727e0d3a6ac3729300e3013930"},{"type":"WEB","url":"https://git.kernel.org/stable/c/17c8d794527f01def0d1c8b7dc2d7b8d34fed0e6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3664ae91b26d1fd7e4cee9cde17301361f4c89d5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/37aed407496bf6de8910e588edb04d2435fa7011"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6b9fb82df8868dbe9ffea5874b8d35f951faedbb"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6eec67bfb25637f9b51e584cf59ddace59925bc8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b638c3fb0f163e69785ceddb3b434a9437878bec"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ca4e51359608e1f29bf1f2c33c3ddf775b6b7ed1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39985.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39985"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"51f3baad7de943780ce0c17bd7975df567dd6e14"},{"fixed":"0fa9303c4b9493727e0d3a6ac3729300e3013930"},{"fixed":"37aed407496bf6de8910e588edb04d2435fa7011"},{"fixed":"6eec67bfb25637f9b51e584cf59ddace59925bc8"},{"fixed":"ca4e51359608e1f29bf1f2c33c3ddf775b6b7ed1"},{"fixed":"3664ae91b26d1fd7e4cee9cde17301361f4c89d5"},{"fixed":"6b9fb82df8868dbe9ffea5874b8d35f951faedbb"},{"fixed":"b638c3fb0f163e69785ceddb3b434a9437878bec"},{"fixed":"17c8d794527f01def0d1c8b7dc2d7b8d34fed0e6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39985.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.12.0"},{"fixed":"5.4.300"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.5.0"},{"fixed":"5.10.245"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.194"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.155"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.109"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.50"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.16.10"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39985.json"}}],"schema_version":"1.7.5"}