{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-39985", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.150Z", "datePublished": "2025-10-15T07:56:04.439Z", "dateUpdated": "2026-08-05T12:06:52.589Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:06:52.589Z" }, "descriptions": [ { "lang": "en", "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/net/can/usb/mcba_usb.c" ], "versions": [ { "version": "51f3baad7de943780ce0c17bd7975df567dd6e14", "lessThan": "0fa9303c4b9493727e0d3a6ac3729300e3013930", "status": "affected", "versionType": "git" }, { "version": "51f3baad7de943780ce0c17bd7975df567dd6e14", "lessThan": "37aed407496bf6de8910e588edb04d2435fa7011", "status": "affected", "versionType": "git" }, { "version": "51f3baad7de943780ce0c17bd7975df567dd6e14", "lessThan": "6eec67bfb25637f9b51e584cf59ddace59925bc8", "status": "affected", "versionType": "git" }, { "version": "51f3baad7de943780ce0c17bd7975df567dd6e14", "lessThan": "ca4e51359608e1f29bf1f2c33c3ddf775b6b7ed1", "status": "affected", "versionType": "git" }, { "version": "51f3baad7de943780ce0c17bd7975df567dd6e14", "lessThan": "3664ae91b26d1fd7e4cee9cde17301361f4c89d5", "status": "affected", "versionType": "git" }, { "version": "51f3baad7de943780ce0c17bd7975df567dd6e14", "lessThan": "6b9fb82df8868dbe9ffea5874b8d35f951faedbb", "status": "affected", "versionType": "git" }, { "version": "51f3baad7de943780ce0c17bd7975df567dd6e14", "lessThan": "b638c3fb0f163e69785ceddb3b434a9437878bec", "status": "affected", "versionType": "git" }, { "version": "51f3baad7de943780ce0c17bd7975df567dd6e14", "lessThan": "17c8d794527f01def0d1c8b7dc2d7b8d34fed0e6", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/net/can/usb/mcba_usb.c" ], "versions": [ { "version": "4.12", "status": "affected" }, { "version": "0", "lessThan": "4.12", "status": "unaffected", "versionType": "semver" }, { "version": "5.4.300", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.245", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.194", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.155", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.109", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.50", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.16.10", "lessThanOrEqual": "6.16.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.17", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.12", "versionEndExcluding": "5.4.300" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.12", "versionEndExcluding": "5.10.245" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.12", "versionEndExcluding": "5.15.194" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.12", "versionEndExcluding": "6.1.155" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.12", "versionEndExcluding": "6.6.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.12", "versionEndExcluding": "6.12.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.12", "versionEndExcluding": "6.16.10" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.12", "versionEndExcluding": "6.17" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/0fa9303c4b9493727e0d3a6ac3729300e3013930" }, { "url": "https://git.kernel.org/stable/c/37aed407496bf6de8910e588edb04d2435fa7011" }, { "url": "https://git.kernel.org/stable/c/6eec67bfb25637f9b51e584cf59ddace59925bc8" }, { "url": "https://git.kernel.org/stable/c/ca4e51359608e1f29bf1f2c33c3ddf775b6b7ed1" }, { "url": "https://git.kernel.org/stable/c/3664ae91b26d1fd7e4cee9cde17301361f4c89d5" }, { "url": "https://git.kernel.org/stable/c/6b9fb82df8868dbe9ffea5874b8d35f951faedbb" }, { "url": "https://git.kernel.org/stable/c/b638c3fb0f163e69785ceddb3b434a9437878bec" }, { "url": "https://git.kernel.org/stable/c/17c8d794527f01def0d1c8b7dc2d7b8d34fed0e6" } ], "title": "can: mcba_usb: populate ndo_change_mtu() to prevent buffer overflow", "x_generator": { "engine": "bippy-1.2.0" } } } }