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

Type: advisorySource: Official CVE List1 source record

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.

Announced Source revision 1
Original source ↗

CVE-2026-80905

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-80905

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "8c76e77f9069f10505c08e02646c3ee11ad79038",
        "lessThan": "c0376820922d255ae1d103c32345a6ec4c3266f7",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8c76e77f9069f10505c08e02646c3ee11ad79038",
        "lessThan": "f1d297cad5c1eacd9fadfd0346ad97405ffbf97c",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8c76e77f9069f10505c08e02646c3ee11ad79038",
        "lessThan": "5ffaa5d7f56ab24a8e23cf131eadfef31a3bbc4b",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8c76e77f9069f10505c08e02646c3ee11ad79038",
        "lessThan": "88b79ac89ecc04d7f2613f7e1c0b46f0c4ddb2f3",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8c76e77f9069f10505c08e02646c3ee11ad79038",
        "lessThan": "cbb35cbe8db268fefe34c23df15348cf99025298",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3cae5ef1f37a475faf7c40bc6a3c170779f3e0b1",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "4.20.1",
        "lessThan": "4.21",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "drivers/net/tap.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.0"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.0",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "6.6.160",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.114",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.46",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.1.10",
        "versionType": "semver",
        "lessThanOrEqual": "7.1.*"
      },
      {
        "status": "unaffected",
        "version": "7.2",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "drivers/net/tap.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-80905

Source reference: /cveMetadata/cveId

Publisher severity

No explicit severity was provided.

Event
#46645 · Revision 1
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