{"id":"CVE-2026-80905","state":"PUBLISHED","title":"net: tap: fix wrong transport_header when sending VLAN-tagged frame","description":"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->protocol 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.","publishedAt":"2026-09-04T17:19:15.289Z","updatedAt":"2026-10-30T12:31:24.447Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"a8f49e83e4447b885376e6a937d62df883cc8824","versionType":"git"},{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"c0376820922d255ae1d103c32345a6ec4c3266f7","versionType":"git"},{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"f1d297cad5c1eacd9fadfd0346ad97405ffbf97c","versionType":"git"},{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b","versionType":"git"},{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3","versionType":"git"},{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"cbb35cbe8db268fefe34c23df15348cf99025298","versionType":"git"},{"version":"3cae5ef1f37a475faf7c40bc6a3c170779f3e0b1","status":"affected","versionType":"git"},{"version":"4.20.1","status":"affected","lessThan":"4.21","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/tap.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.0","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.46","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.10","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/tap.c"]}],"references":["https://git.kernel.org/stable/c/a8f49e83e4447b885376e6a937d62df883cc8824","https://git.kernel.org/stable/c/c0376820922d255ae1d103c32345a6ec4c3266f7","https://git.kernel.org/stable/c/f1d297cad5c1eacd9fadfd0346ad97405ffbf97c","https://git.kernel.org/stable/c/5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b","https://git.kernel.org/stable/c/88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3","https://git.kernel.org/stable/c/cbb35cbe8db268fefe34c23df15348cf99025298"],"weaknesses":[],"ingestedAt":"2026-10-30T12:50:04.827Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/80xxx/CVE-2026-80905.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-80905","state":"PUBLISHED","datePublished":"2026-09-04T17:19:15.289Z","dateUpdated":"2026-10-30T12:31:24.447Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-26T14:34:25.800Z"},"containers":{"cna":{"title":"net: tap: fix wrong transport_header when sending VLAN-tagged frame","descriptions":[{"lang":"en","value":"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->protocol 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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"a8f49e83e4447b885376e6a937d62df883cc8824","versionType":"git"},{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"c0376820922d255ae1d103c32345a6ec4c3266f7","versionType":"git"},{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"f1d297cad5c1eacd9fadfd0346ad97405ffbf97c","versionType":"git"},{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b","versionType":"git"},{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3","versionType":"git"},{"version":"8c76e77f9069f10505c08e02646c3ee11ad79038","status":"affected","lessThan":"cbb35cbe8db268fefe34c23df15348cf99025298","versionType":"git"},{"version":"3cae5ef1f37a475faf7c40bc6a3c170779f3e0b1","status":"affected","versionType":"git"},{"version":"4.20.1","status":"affected","lessThan":"4.21","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/tap.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.0","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.46","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.10","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/tap.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/a8f49e83e4447b885376e6a937d62df883cc8824"},{"url":"https://git.kernel.org/stable/c/c0376820922d255ae1d103c32345a6ec4c3266f7"},{"url":"https://git.kernel.org/stable/c/f1d297cad5c1eacd9fadfd0346ad97405ffbf97c"},{"url":"https://git.kernel.org/stable/c/5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b"},{"url":"https://git.kernel.org/stable/c/88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3"},{"url":"https://git.kernel.org/stable/c/cbb35cbe8db268fefe34c23df15348cf99025298"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:31:24.447Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"6.18.46"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"7.1.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.0","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.20.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}