CVE-2026-80906: Linux Vulnerability

Description

In the Linux kernel, the following vulnerability has been resolved: net: packet: fix wrong transport_header when sending VLAN-tagged frame In packet_parse_headers(), when processing a VLAN-tagged frame, skb_set_network_header() is called 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 the outer VLAN EtherType (e.g. 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 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_probe_transport_header() to before skb_set_network_header(). At the time skb_probe_transport_header() is called, network_header still points to the VLAN header, so nhoff correctly points to the VLAN header. The flow dissector can then parse the VLAN header, extract the inner EtherType, and advance nhoff to the inner protocol header, allowing transport_header to be set correctly.

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= c2137d565ceb505de69593c181a0543bc4083838, < a4b82de96d465ddb44bc931145c0fa80c4fe9c9c; >= 9ff46c36df2e0a1ac352f2f4038eaf3f0f7361b8, < fa86bc52ea8ba981f74f851fd61e2a3d3bc0feac; >= dfed913e8b55a0c2c4906f1242fd38fd9a116e49, < 5479eb9b355f44745d7ccfe112386bd4f96eceea; >= dfed913e8b55a0c2c4906f1242fd38fd9a116e49, < e451e20adb869a983a21dda158625f024142e61f; >= dfed913e8b55a0c2c4906f1242fd38fd9a116e49, < 6971cf319263d6a1b4096f9248aca9e57d77a1eb; >= dfed913e8b55a0c2c4906f1242fd38fd9a116e49, < f9297abbcaba760b7a7b9d63b839f607f738013e; >= dfed913e8b55a0c2c4906f1242fd38fd9a116e49, < 6386a6ffa2efba2965ed8e4fa303582c0b76a215; >= dfed913e8b55a0c2c4906f1242fd38fd9a116e49, < 01fdecc0480d916c799dbee584833a4a37e94d06; ad3f90a9c4a2c74bb3711f2031bffda4ec44c849; >= 5.10.163, < 5.10.266; >= 5.15.87, < 5.15.217; >= 5.4.229, < 5.5
Linux	Linux	5.19

References

Timeline

Published: Sep 4, 2026
Last Modified: Sep 4, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-80906?

In the Linux kernel, the following vulnerability has been resolved: net: packet: fix wrong transport_header when sending VLAN-tagged frame In packet_parse_headers(), when processing a VLAN-tagged frame, skb_set_network_header() is called 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 the outer VLAN EtherType (e.g. 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 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_probe_transport_header() to before skb_set_network_header(). At the time skb_probe_transport_header() is called, network_header still points to the VLAN header, so nhoff correctly points to the VLAN header. The flow dissector can then parse the VLAN header, extract the inner EtherType, and advance nhoff to the inner protocol header, allowing transport_header to be set correctly.

How severe is CVE-2026-80906?

Severity scoring for CVE-2026-80906 is pending analysis.

How do I fix CVE-2026-80906?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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