CVE-2026-80905 - Vulnerability Details

Vendors	Products
Linux	Linux Kernel

Link	Providers
https://git.kernel.org/stable/c/5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b
https://git.kernel.org/stable/c/88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3
https://git.kernel.org/stable/c/cbb35cbe8db268fefe34c23df15348cf99025298

Type	Values Removed	Values Added
Weaknesses		CWE-665

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: net: tap: fix wrong transport_header when sending VLAN-tagged frame In tap_get_user_xdp(), when processing a VLAN-tagged frame (e.g. ETH_P_8021Q), skb_set_network_header() is called first to advance network_header past the VLAN tag to the inner protocol header. skb_probe_transport_header() is then called with skb->protocol still set to ETH_P_8021Q, while nhoff (derived from skb_network_offset()) already points past the VLAN tag to the inner protocol header. In __skb_flow_dissect(), proto is initialized to ETH_P_8021Q and nhoff points past the VLAN tag. When the dissector hits case ETH_P_8021Q, it reads a struct vlan_hdr at the current nhoff via __skb_header_pointer(), but that offset contains the inner protocol header (e.g. an IP header). The bytes are misinterpreted as a VLAN header, yielding a garbage encapsulated EtherType that matches no known protocol. The dissector returns false, so skb_probe_transport_header() never calls skb_set_transport_header(), leaving transport_header at its uninitialized sentinel value (~0U). Move skb_set_network_header() to after skb_probe_transport_header(). At the time skb_probe_transport_header() is called, network_header still points to the VLAN header (offset ETH_HLEN), so nhoff is correct and the flow dissector can parse the VLAN header, extract the inner EtherType, and advance nhoff to the inner protocol header, allowing transport_header to be set correctly.
Title		net: tap: fix wrong transport_header when sending VLAN-tagged frame
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b https://git.kernel.org/stable/c/88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3 https://git.kernel.org/stable/c/cbb35cbe8db268fefe34c23df15348cf99025298

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-80905", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-26T14:34:25.800Z", "datePublished": "2026-09-04T17:19:15.289Z", "dateUpdated": "2026-09-04T17:19:15.289Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-09-04T17:19:15.289Z"}, "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": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["drivers/net/tap.c"], "versions": [{"version": "8c76e77f9069f10505c08e02646c3ee11ad79038", "lessThan": "5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b", "status": "affected", "versionType": "git"}, {"version": "8c76e77f9069f10505c08e02646c3ee11ad79038", "lessThan": "88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3", "status": "affected", "versionType": "git"}, {"version": "8c76e77f9069f10505c08e02646c3ee11ad79038", "lessThan": "cbb35cbe8db268fefe34c23df15348cf99025298", "status": "affected", "versionType": "git"}, {"version": "3cae5ef1f37a475faf7c40bc6a3c170779f3e0b1", "status": "affected", "versionType": "git"}, {"version": "4.20.1", "lessThan": "4.21", "status": "affected", "versionType": "semver"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["drivers/net/tap.c"], "versions": [{"version": "5.0", "status": "affected"}, {"version": "0", "lessThan": "5.0", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.46", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.1.10", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2", "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": "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"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b"}, {"url": "https://git.kernel.org/stable/c/88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3"}, {"url": "https://git.kernel.org/stable/c/cbb35cbe8db268fefe34c23df15348cf99025298"}], "title": "net: tap: fix wrong transport_header when sending VLAN-tagged frame", "x_generator": {"engine": "bippy-1.2.0"}}}}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["drivers/net/tap.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b", "status": "affected", "version": "8c76e77f9069f10505c08e02646c3ee11ad79038", "versionType": "git"}, {"lessThan": "88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3", "status": "affected", "version": "8c76e77f9069f10505c08e02646c3ee11ad79038", "versionType": "git"}, {"lessThan": "cbb35cbe8db268fefe34c23df15348cf99025298", "status": "affected", "version": "8c76e77f9069f10505c08e02646c3ee11ad79038", "versionType": "git"}, {"status": "affected", "version": "3cae5ef1f37a475faf7c40bc6a3c170779f3e0b1", "versionType": "git"}, {"lessThan": "4.21", "status": "affected", "version": "4.20.1", "versionType": "semver"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["drivers/net/tap.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "5.0"}, {"lessThan": "5.0", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.46", "versionType": "semver"}, {"lessThanOrEqual": "7.1.*", "status": "unaffected", "version": "7.1.10", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.2", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "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."}], "id": "CVE-2026-80905", "lastModified": "2026-09-04T18:18:00.120", "metrics": {}, "published": "2026-09-04T18:18:00.120", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/cbb35cbe8db268fefe34c23df15348cf99025298"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

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