{"id":"CVE-2025-39986","summary":"can: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ncan: sun4i_can: 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, sun4ican_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 this line:\n\n\tdlc = cf-\u003elen;\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 a\ncouple line below when doing:\n\n\tfor (i = 0; i \u003c dlc; i++)\n\t\twritel(cf-\u003edata[i], priv-\u003ebase + (dreg + i * 4));\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":"2026-04-16T04:30:35.221686035Z","published":"2025-10-15T07:56:05.143Z","related":["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":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39986.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/063539db42203b29d5aa2adf0cae3d68c646a6b6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2e423e1990f3972cbea779883fef52c2f2acb858"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4f382cc887adca8478b9d3e6b81aa6698a95fff4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/60463a1c138900494cb3adae41142a11cd8feb3c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/61da0bd4102c459823fbe6b8b43b01fb6ace4a22"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7f7b21026a6febdb749f6f6f950427245aa86cce"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a61ff7ac93270d20ca426c027d6d01c8ac8e904c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/de77841652e57afbc46e9e1dbf51ee364fc008e1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39986.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39986"},{"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":"0738eff14d817a02ab082c392c96a1613006f158"},{"fixed":"063539db42203b29d5aa2adf0cae3d68c646a6b6"},{"fixed":"4f382cc887adca8478b9d3e6b81aa6698a95fff4"},{"fixed":"60463a1c138900494cb3adae41142a11cd8feb3c"},{"fixed":"a61ff7ac93270d20ca426c027d6d01c8ac8e904c"},{"fixed":"2e423e1990f3972cbea779883fef52c2f2acb858"},{"fixed":"de77841652e57afbc46e9e1dbf51ee364fc008e1"},{"fixed":"7f7b21026a6febdb749f6f6f950427245aa86cce"},{"fixed":"61da0bd4102c459823fbe6b8b43b01fb6ace4a22"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39986.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.4.0"},{"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-2025-39986.json"}}],"schema_version":"1.7.5"}