CVE-2026-80906

Summary

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

VendorProductVersion RangeStatus
LinuxLinuxc2137d565ceb505de69593c181a0543bc4083838 < a4b82de96d465ddb44bc931145c0fa80c4fe9c9caffected
LinuxLinux9ff46c36df2e0a1ac352f2f4038eaf3f0f7361b8 < fa86bc52ea8ba981f74f851fd61e2a3d3bc0feacaffected
LinuxLinuxdfed913e8b55a0c2c4906f1242fd38fd9a116e49 < 5479eb9b355f44745d7ccfe112386bd4f96eceeaaffected
LinuxLinuxdfed913e8b55a0c2c4906f1242fd38fd9a116e49 < e451e20adb869a983a21dda158625f024142e61faffected
LinuxLinuxdfed913e8b55a0c2c4906f1242fd38fd9a116e49 < 6971cf319263d6a1b4096f9248aca9e57d77a1ebaffected
LinuxLinuxdfed913e8b55a0c2c4906f1242fd38fd9a116e49 < f9297abbcaba760b7a7b9d63b839f607f738013eaffected
LinuxLinuxdfed913e8b55a0c2c4906f1242fd38fd9a116e49 < 6386a6ffa2efba2965ed8e4fa303582c0b76a215affected
LinuxLinuxdfed913e8b55a0c2c4906f1242fd38fd9a116e49 < 01fdecc0480d916c799dbee584833a4a37e94d06affected
LinuxLinuxad3f90a9c4a2c74bb3711f2031bffda4ec44c849affected
LinuxLinux5.10.163 < 5.10.266affected
LinuxLinux5.15.87 < 5.15.217affected
LinuxLinux5.4.229 < 5.5affected
LinuxLinux5.19affected
LinuxLinux0 < 5.19unaffected
LinuxLinux5.10.266 <= 5.10.*unaffected
LinuxLinux5.15.217 <= 5.15.*unaffected
LinuxLinux6.1.184 <= 6.1.*unaffected
LinuxLinux6.6.153 <= 6.6.*unaffected
LinuxLinux6.12.105 <= 6.12.*unaffected
LinuxLinux6.18.46 <= 6.18.*unaffected
LinuxLinux7.1.10 <= 7.1.*unaffected
LinuxLinux7.2 <= *unaffected

Weaknesses

References