CVE-2026-80905

/// Technical 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(

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References