{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-39986", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.150Z", "datePublished": "2025-10-15T07:56:05.143Z", "dateUpdated": "2026-08-05T12:06:53.662Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:06:53.662Z" }, "descriptions": [ { "lang": "en", "value": "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->len fits the interface's MTU.\n\nUnfortunately, because the sun4i_can 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, 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->len\nas-is with no further checks on this line:\n\n\tdlc = cf->len;\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 a\ncouple line below when doing:\n\n\tfor (i = 0; i < dlc; i++)\n\t\twritel(cf->data[i], priv->base + (dreg + i * 4));\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 - Triggering requires local syscalls on the host — `socket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL))` followed by `sendmsg()` to the can interface, reaching `sun4ican_start_xmit()` through `dev_queue_xmit()`. The bug is entirely in the TX path; a remote or adjacent CAN-bus peer is only the sink and cannot reach it.\nAC:L - The overflow is fully deterministic — `can_dropped_invalid_skb()` accepts an ETH_P_CANXL skb on a classic-CAN device, `canxl_frame.flags` is reinterpreted as `can_frame.len`, and the loop unconditionally walks up to 255 elements. No race, no memory-layout guessing, and no condition outside the attacker's control is involved.\nPR:L - The only gate is `ns_capable(net->user_ns, CAP_NET_RAW)` in `packet_create()`, which is namespaced and granted by default in common container runtimes; because a 13–16 byte CAN XL frame already passes the default CAN_MTU check, the CAP_NET_ADMIN MTU change is not even needed. CAN netdevs are not netns-local, so a `can0` delegated into a container/user namespace lets an otherwise unprivileged user trigger this with no real root.\nUI:N - The attacker performs every step alone — open the packet socket and send one malicious CAN XL frame to an up CAN interface. No victim action, no configuration change by an administrator, and no interaction of any kind is required.\nS:U - The out-of-bounds read and the runaway MMIO writes stay within the kernel of the same host; no VM, hypervisor, or IOMMU boundary is crossed. The vulnerable component and the impacted resources share a single security authority.\nC:H - With a minimal 13–16 byte skb the loop reads `cf->data[0..254]`, over-reading roughly 247 bytes of adjacent kernel heap past the packet data. That residue is pushed into the controller's registers and, with self-reception/loopback enabled, bytes beyond `skb->len` are echoed back to userspace, giving a repeatable kernel-memory disclosure primitive.\nI:H - Up to 254 attacker-influenced 32-bit stores land beyond the intended 8-byte TX buffer slot, overwriting the entire sun4i CAN register block (acceptance/readback/reserved registers) with out-of-bounds heap contents. This is a controlled out-of-bounds write that corrupts device state and, past `0x400`, writes to memory outside the ioremap mapping entirely.\nA:H - For `dlc` above 235 the write offset exceeds the `0x400` ioremap window, and since the mapping ends exactly on a page boundary the next page is the vmalloc guard page — an unmapped kernel VA store that produces an immediate oops/panic. The condition is re-triggerable at will from an unprivileged socket, and the register scribbling wedges the CAN controller even when the fault is avoided." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/net/can/sun4i_can.c" ], "versions": [ { "version": "0738eff14d817a02ab082c392c96a1613006f158", "lessThan": "063539db42203b29d5aa2adf0cae3d68c646a6b6", "status": "affected", "versionType": "git" }, { "version": "0738eff14d817a02ab082c392c96a1613006f158", "lessThan": "4f382cc887adca8478b9d3e6b81aa6698a95fff4", "status": "affected", "versionType": "git" }, { "version": "0738eff14d817a02ab082c392c96a1613006f158", "lessThan": "60463a1c138900494cb3adae41142a11cd8feb3c", "status": "affected", "versionType": "git" }, { "version": "0738eff14d817a02ab082c392c96a1613006f158", "lessThan": "a61ff7ac93270d20ca426c027d6d01c8ac8e904c", "status": "affected", "versionType": "git" }, { "version": "0738eff14d817a02ab082c392c96a1613006f158", "lessThan": "2e423e1990f3972cbea779883fef52c2f2acb858", "status": "affected", "versionType": "git" }, { "version": "0738eff14d817a02ab082c392c96a1613006f158", "lessThan": "de77841652e57afbc46e9e1dbf51ee364fc008e1", "status": "affected", "versionType": "git" }, { "version": "0738eff14d817a02ab082c392c96a1613006f158", "lessThan": "7f7b21026a6febdb749f6f6f950427245aa86cce", "status": "affected", "versionType": "git" }, { "version": "0738eff14d817a02ab082c392c96a1613006f158", "lessThan": "61da0bd4102c459823fbe6b8b43b01fb6ace4a22", "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/sun4i_can.c" ], "versions": [ { "version": "4.4", "status": "affected" }, { "version": "0", "lessThan": "4.4", "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": "4.4", "versionEndExcluding": "5.4.300" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "5.10.245" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "5.15.194" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.1.155" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.6.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.12.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.16.10" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.4", "versionEndExcluding": "6.17" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/063539db42203b29d5aa2adf0cae3d68c646a6b6" }, { "url": "https://git.kernel.org/stable/c/4f382cc887adca8478b9d3e6b81aa6698a95fff4" }, { "url": "https://git.kernel.org/stable/c/60463a1c138900494cb3adae41142a11cd8feb3c" }, { "url": "https://git.kernel.org/stable/c/a61ff7ac93270d20ca426c027d6d01c8ac8e904c" }, { "url": "https://git.kernel.org/stable/c/2e423e1990f3972cbea779883fef52c2f2acb858" }, { "url": "https://git.kernel.org/stable/c/de77841652e57afbc46e9e1dbf51ee364fc008e1" }, { "url": "https://git.kernel.org/stable/c/7f7b21026a6febdb749f6f6f950427245aa86cce" }, { "url": "https://git.kernel.org/stable/c/61da0bd4102c459823fbe6b8b43b01fb6ace4a22" } ], "title": "can: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow", "x_generator": { "engine": "bippy-1.2.0" } } } }