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CVE PROGRAM SOURCE RECORDUnscored

CVE-2026-80905

net: tap: fix wrong transport_header when sending VLAN-tagged frame

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Status
Published
Published
Updated
Assigning organization
Linux

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 8c76e77f9069f10505c08e02646c3ee11ad79038 to < c0376820922d255ae1d103c32345a6ec4c3266f7affected
  • 8c76e77f9069f10505c08e02646c3ee11ad79038 to < f1d297cad5c1eacd9fadfd0346ad97405ffbf97caffected
  • 8c76e77f9069f10505c08e02646c3ee11ad79038 to < 5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4baffected
  • 8c76e77f9069f10505c08e02646c3ee11ad79038 to < 88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3affected
  • 8c76e77f9069f10505c08e02646c3ee11ad79038 to < cbb35cbe8db268fefe34c23df15348cf99025298affected
  • 3cae5ef1f37a475faf7c40bc6a3c170779f3e0b1affected
  • 4.20.1 to < 4.21affected

Linux Linux

Default version status: affected

  • 5.0affected
  • 0 to < 5.0unaffected
  • 6.6.160 to ≤ 6.6.*unaffected
  • 6.12.114 to ≤ 6.12.*unaffected
  • 6.18.46 to ≤ 6.18.*unaffected
  • 7.1.10 to ≤ 7.1.*unaffected
  • 7.2 to ≤ *unaffected

References