macsec: don't read an unset MAC header in macsec_encrypt()

{
  "id": "d1095c9cd5c6798c2567e23425cf2d607b4388f8916fcf09f6590da0b5b4a574",
  "url": "https://osv.dev/vulnerability/CVE-2026-72019",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "macsec: don't read an unset MAC header in macsec_encrypt()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: macsec: don't read an unset MAC header in macsec_encrypt() macsec_encrypt() reads the Ethernet header via eth_hdr(skb) (skb->head + skb->mac_header) to memmove() the 12 source/destination MAC bytes forward and make room for the SecTAG. On the AF_PACKET SOCK_RAW + PACKET_QDISC_BYPASS transmit path the skb reaches the macsec ndo_start_xmit() with the MAC header unset, so eth_hdr(skb) resolves to skb->head + (u16)~0 and the read is out of bounds: a 12-byte heap over-read that is also emitted on the wire as the frame's outer source/destination MAC. KASAN reports a slab-out-of-bounds read in macsec_start_xmit() on 6.0; on current mainline a CONFIG_DEBUG_NET build flags it as an unset mac header in skb_mac_header(). On the TX path the L2 header is at skb->data, so use skb_eth_hdr(), added by commit 96cc4b69581d (\"macvlan: do not assume mac_header is set in macvlan_broadcast()\") for exactly this purpose.",
    "evidence": "osv:CVE-2026-72019",
    "products": [
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          "value": "Kernel",
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        "prerequisites": [],
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    "severity": "high",
    "structured": {
      "id": "CVE-2026-72019",
      "aliases": [
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      "metrics": [
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          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H"
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      "modified": "2026-10-28T02:30:36.832059831Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/2cf10d042562283ff4ae97c02d0993d4f1b5ea29",
        "https://git.kernel.org/stable/c/3adea1b1c04b57e08a5c12a1f42483760581ce61",
        "https://git.kernel.org/stable/c/b6cec6187b8632423cd99a94fd5e5ba165fa2a33",
        "https://git.kernel.org/stable/c/c39087ad0b97fc11a3b058dfc8db9fd370762cb9",
        "https://git.kernel.org/stable/c/dc9ffa1905e72f026d080880a2e4cfc42aa91000",
        "https://git.kernel.org/stable/c/e17a42199824973cd8212e95b21ffadf4114a21b",
        "https://git.kernel.org/stable/c/f21fa533a3ed15ada74106aac4b9ddd078fc6b7a",
        "https://git.kernel.org/stable/c/f5089008f90c0a7c5520dff3934e0af00adf322d",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72019.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-72019",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72019.json"
      }
    },
    "related_cves": [
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        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504352,
  "published_at": "2026-08-15T05:51:46.014+00:00"
}