264 lines
16 KiB
JSON
264 lines
16 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2025-39985",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2025-04-16T07:20:57.150Z",
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"datePublished": "2025-10-15T07:56:04.439Z",
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"dateUpdated": "2026-08-05T12:06:52.589Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-08-05T12:06:52.589Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "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->len fits the interface's MTU.\n\nUnfortunately, because the mcba_usb driver does not populate its\nnet_device_ops->ndo_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->protocol 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->len\nas-is with no further checks on these lines:\n\n\tusb_msg.dlc = cf->len;\n\n\tmemcpy(usb_msg.data, cf->data, usb_msg.dlc);\n\nHere, cf->len corresponds to the flags field of the CAN XL frame. In\nour previous example, we set canxl_frame->flags to 0xff. Because the\nmaximum expected length is 8, a buffer overflow of 247 bytes occurs!\n\nPopulate net_device_ops->ndo_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."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:L - Exploitation is performed entirely with local syscalls on the host owning the CAN interface — `socket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL))` plus `sendmsg()`, optionally preceded by an rtnetlink MTU change. No remote or adjacent-network peer can reach `mcba_usb_start_xmit()`; the USB dongle and the CAN bus are only the sink for the resulting transfer, never the source of the malicious frame.\nAC:L - The overflow is fully deterministic — a single crafted CAN XL frame with `flags = 0xff` unconditionally makes `cf->len` 255 and drives a 255-byte `memcpy()` into an 8-byte stack field, with no race, no timing window, and no dependence on memory layout to trigger.\nPR:L - The minimal variant needs only `ns_capable(net->user_ns, CAP_NET_RAW)` from `packet_create()` because a 13–16 byte CAN XL skb already fits under the default `CAN_MTU`, and the fully-controlled-payload variant adds only the namespaced `CAP_NET_ADMIN` for the MTU change; CAN netdevs are not netns-local, so a `can0` delegated into a container or user namespace puts both capabilities in the hands of an unprivileged user, and typical container runtimes grant `CAP_NET_RAW` by default.\nUI:N - The attacker performs every step alone — open the packet socket, optionally set the MTU, and send the malicious CAN XL frame. No victim action, mount, or file open is involved.\nS:U - The corruption stays in kernel stack and adjacent heap memory within the same kernel security authority as the attacking process; no VM, hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - With a minimal 13-byte skb permitted at the default MTU, the `memcpy()` reads 255 bytes from a much smaller skb data area, over-reading ~247 bytes of adjacent kernel heap, and 8 of those bytes are copied into the URB and DMA'd out to the USB device as an externally observable disclosure primitive; the stack corruption itself further yields arbitrary-read capability.\nI:H - Up to 247 bytes are written past an 8-byte array in a 19-byte stack struct, overwriting the stack canary, saved registers and return address of `mcba_usb_start_xmit()`, and with the MTU raised those bytes are entirely attacker-chosen — a classic control-flow hijack and arbitrary-write primitive suitable for privilege escalation.\nA:H - The stack smash trips the stack protector (`__stack_chk_fail` panic) or corrupts the transmitting task's frame in the xmit path, reliably producing a kernel oops or panic, and it can be re-triggered at will from an unprivileged socket."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"drivers/net/can/usb/mcba_usb.c"
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],
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"versions": [
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{
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{
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"drivers/net/can/usb/mcba_usb.c"
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],
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{
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"url": "https://git.kernel.org/stable/c/6eec67bfb25637f9b51e584cf59ddace59925bc8"
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},
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{
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"url": "https://git.kernel.org/stable/c/ca4e51359608e1f29bf1f2c33c3ddf775b6b7ed1"
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},
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{
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},
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{
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"url": "https://git.kernel.org/stable/c/6b9fb82df8868dbe9ffea5874b8d35f951faedbb"
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}
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],
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"title": "can: mcba_usb: populate ndo_change_mtu() to prevent buffer overflow",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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}
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}
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} |