Evidence-led vulnerability intelligence · 2026-09-04 23:48 IST

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.

UNRATED · N/ALinux

Executive briefing

The source record describes: 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. The practical risk depends on whether an affected product/version is present, reachable and configured in an exploitable way. Review the affected-product evidence and linked vendor advisories before assigning exposure status.

Assessment: Potential exposure only — validate the installed product, exact version, configuration and vendor applicability before treating an asset as confirmed vulnerable.

Evidence confidence: Low Evidence-derived, not an exploitability verdict

Severity & attack characteristics

N/A / 10 ·

CVSS vector:

No CVSS vector is currently available in the source record.

Technical explanation & impact

The technical mechanism is not expanded beyond the source description unless a referenced advisory supplies additional evidence. Read the linked vendor/CERT advisories for root-cause detail.

Potential impact must be interpreted from the published CVSS impact metrics and the affected component. A CVSS impact score is not proof that a particular asset is exploitable.

Affected products and versions

NVD has not supplied machine-readable vulnerable CPE product/version entries for this CVE. This is an information gap, not proof that no products are affected. Check the vendor advisory references below.

Remediation & validation

  1. Identify exposure by comparing the affected product and version ranges with your asset inventory, SBOM and externally exposed services.
  2. Review the linked vendor security advisory or patch notes. Upgrade to a vendor-confirmed fixed release; do not infer a fixed version from the CVE description.
  3. Until patched, consider restricting network access or disabling the affected feature where operationally safe. These are temporary controls, not a substitute for a vendor fix.
  4. Validate the remediation with a version check and vulnerability rescan, then retain change evidence.

No fixed version is displayed unless it is explicitly established by a vendor advisory. Follow the vendor's release notes for exact product and branch applicability.

Vendor advisories, patches & exploit references

Information gaps & confidence notes

These gaps indicate missing source data. CVE Watch does not fill them with guessed product, exploit or patch details.

Last enrichment: 2026-11-07T17:03:31+00:00 · Source last modified: 2026-11-06T17:20:01.703

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