{"id":"CVE-2026-72444","title":"flow_dissector: check device type before reading ETH_ADDRS","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nflow_dissector: check device type before reading ETH_ADDRS\n\n__skb_flow_dissect() unconditionally reads 12 bytes from eth_hdr(skb)\nwhen FLOW_DISSECTOR_KEY_ETH_ADDRS is r…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 67a900cc0436d74e7ff89042371760def087680d < 0fe6455b8e1a22414f39c07bc90a1df12b52ec74","Linux >= 67a900cc0436d74e7ff89042371760def087680d < 9a65860959db594dfc1820c7fdc09285fb7556bf","Linux >= 67a900cc0436d74e7ff89042371760def087680d < 594c90b197141944f25991b8314de5c26ee27a7e","Linux >= 67a900cc0436d74e7ff89042371760def087680d < c6d3bcb0f934d4297ac5fa1c8656ae40694fb601","Linux >= 67a900cc0436d74e7ff89042371760def087680d < 825de39f0c35a112148799b3cbe45af3766c018a","Linux >= 67a900cc0436d74e7ff89042371760def087680d < bf6e8af2c8be77489bedeae9f8a9654cb710e500","Linux 4.2"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T18:50:08.470597Z"},"published":"2026-08-15","updated":"2026-10-16","sourceUpdated":"2026-10-16T18:55:24.524Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-72444","references":[{"url":"https://git.kernel.org/stable/c/0fe6455b8e1a22414f39c07bc90a1df12b52ec74"},{"url":"https://git.kernel.org/stable/c/9a65860959db594dfc1820c7fdc09285fb7556bf"},{"url":"https://git.kernel.org/stable/c/594c90b197141944f25991b8314de5c26ee27a7e"},{"url":"https://git.kernel.org/stable/c/c6d3bcb0f934d4297ac5fa1c8656ae40694fb601"},{"url":"https://git.kernel.org/stable/c/825de39f0c35a112148799b3cbe45af3766c018a"},{"url":"https://git.kernel.org/stable/c/bf6e8af2c8be77489bedeae9f8a9654cb710e500"}],"tags":["cve.org"],"epss":0.00176,"epssPercentile":0.06637,"ingestedAt":"2026-10-16T19:46:24.395Z","slug":"CVE-2026-72444","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nflow_dissector: check device type before reading ETH_ADDRS\n\n__skb_flow_dissect() unconditionally reads 12 bytes from eth_hdr(skb)\nwhen FLOW_DISSECTOR_KEY_ETH_ADDRS is requested. This assumes the skb\nhas a valid Ethernet header at mac_header, which is not always the case.\n\nThe problem can be triggered by:\n 1. Creating a TUN device in L3 mode (IFF_TUN, hard_header_len=0)\n 2. Attaching a multiq qdisc with a flower filter matching on eth_src\n 3. Sending a packet through AF_PACKET\n\nSince TUN in L3 mode has no link-layer header, mac_header points to\nthe L3 data area. The flow dissector reads 12 bytes of uninitialized\nskb memory, which then propagates through fl_set_masked_key() and is\nused as a rhashtable lookup key in __fl_lookup(), as reported by KMSAN.\n\nRejecting the filter in the control path (at tc filter add time) is\nnot feasible because TC filter blocks can be shared between arbitrary\ndevices -- a filter installed on an Ethernet device may later classify\npackets on a headerless device through a shared block. The device\nassociation is not fixed at filter creation time.\n\nFix this by gating the memcpy on dev->type == ARPHRD_ETHER, which\nensures only true Ethernet-framed packets have their addresses read.\nThis is more precise than the previous hard_header_len >= 12 check,\nwhich would incorrectly pass for non-Ethernet link types like IPoIB\n(ARPHRD_INFINIBAND, hard_header_len=24) and FDDI (hard_header_len=21)\nwhose L2 headers are not in Ethernet format. Additionally check\nskb_mac_header_was_set() to guard against the pathological case where\nmac_header is the unset sentinel (~0U), which would cause eth_hdr() to\nreturn a wild pointer.\n\nFor the act_mirred redirect case (Ethernet packet redirected to a\nnon-Ethernet device sharing a TC block), zeroing the key is the correct\nbehavior: the packet is now being classified on the target device, where\nEthernet address matching is not semantically meaningful.\n\nNote: on non-Ethernet devices, the zeroed key will match a filter\nconfigured with all-zero MAC addresses. This is an improvement over the\nprevious behavior where uninitialized memory could randomly match any\nfilter.\n\n## Affected\n\n- `Linux >= 67a900cc0436d74e7ff89042371760def087680d < 0fe6455b8e1a22414f39c07bc90a1df12b52ec74`\n- `Linux >= 67a900cc0436d74e7ff89042371760def087680d < 9a65860959db594dfc1820c7fdc09285fb7556bf`\n- `Linux >= 67a900cc0436d74e7ff89042371760def087680d < 594c90b197141944f25991b8314de5c26ee27a7e`\n- `Linux >= 67a900cc0436d74e7ff89042371760def087680d < c6d3bcb0f934d4297ac5fa1c8656ae40694fb601`\n- `Linux >= 67a900cc0436d74e7ff89042371760def087680d < 825de39f0c35a112148799b3cbe45af3766c018a`\n- `Linux >= 67a900cc0436d74e7ff89042371760def087680d < bf6e8af2c8be77489bedeae9f8a9654cb710e500`\n- `Linux 4.2`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}