{"id":"CVE-2026-80905","summary":"net: tap: fix wrong transport_header when sending VLAN-tagged frame","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: tap: fix wrong transport_header when sending VLAN-tagged frame\n\nIn tap_get_user_xdp(), when processing a VLAN-tagged frame (e.g.\nETH_P_8021Q), skb_set_network_header() is called first to advance\nnetwork_header past the VLAN tag to the inner protocol header.\nskb_probe_transport_header() is then called with skb-\u003eprotocol still\nset to ETH_P_8021Q, while nhoff (derived from skb_network_offset())\nalready points past the VLAN tag to the inner protocol header.\n\nIn __skb_flow_dissect(), proto is initialized to ETH_P_8021Q and nhoff\npoints past the VLAN tag. When the dissector hits case ETH_P_8021Q, it\nreads a struct vlan_hdr at the current nhoff via __skb_header_pointer(),\nbut that offset contains the inner protocol header (e.g. an IP header).\nThe bytes are misinterpreted as a VLAN header, yielding a garbage\nencapsulated EtherType that matches no known protocol. The dissector\nreturns false, so skb_probe_transport_header() never calls\nskb_set_transport_header(), leaving transport_header at its uninitialized\nsentinel value (~0U).\n\nMove skb_set_network_header() to after skb_probe_transport_header(). At\nthe time skb_probe_transport_header() is called, network_header still\npoints to the VLAN header (offset ETH_HLEN), so nhoff is correct and the\nflow dissector can parse the VLAN header, extract the inner EtherType,\nand advance nhoff to the inner protocol header, allowing transport_header\nto be set correctly.","modified":"2026-11-01T02:30:53.356114844Z","published":"2026-09-04T17:19:15.289Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80905.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a8f49e83e4447b885376e6a937d62df883cc8824"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c0376820922d255ae1d103c32345a6ec4c3266f7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cbb35cbe8db268fefe34c23df15348cf99025298"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f1d297cad5c1eacd9fadfd0346ad97405ffbf97c"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80905.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-80905"},{"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":"8c76e77f9069f10505c08e02646c3ee11ad79038"},{"fixed":"a8f49e83e4447b885376e6a937d62df883cc8824"},{"fixed":"c0376820922d255ae1d103c32345a6ec4c3266f7"},{"fixed":"f1d297cad5c1eacd9fadfd0346ad97405ffbf97c"},{"fixed":"5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b"},{"fixed":"88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3"},{"fixed":"cbb35cbe8db268fefe34c23df15348cf99025298"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.20.1"},{"fixed":"4.21"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3cae5ef1f37a475faf7c40bc6a3c170779f3e0b1"}]}],"versions":["v4.20.17","v4.20.16","v4.20.15","v4.20.14","v4.20.13","v4.20.12","v4.20.11","v4.20.10","v4.20.9","v4.20.8","v4.20.7","v4.20.6","v4.20.5","v4.20.4","v4.20.3","v4.20.2","v4.20.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80905.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.0.0"},{"fixed":"6.1.191"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.160"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.114"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.46"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.10"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80905.json"}}],"schema_version":"1.9.2"}