CVE-2026-80905

CVE CVE-2026-80905EUVD EUVD-2026-71664Published 2026-09-04T17:19:15.000Z

What the advisory describes

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.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux 4.20.1 <4.21; patch: 0; patch: 6.18.46; 5.0; 8c76e77f9069f10505c08e02646c3ee11ad79038 <5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b; 8c76e77f9069f10505c08e02646c3ee11ad79038 <88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3; 8c76e77f9069f10505c08e02646c3ee11ad79038 <cbb35cbe8db268fefe34c23df15348cf99025298; patch: 7.2; patch: 7.1.10; 3cae5ef1f37a475faf7c40bc6a3c170779f3e0b1

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

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