apparmor: mediate the implicit connect of TCP fast open sendmsg

{
  "id": "a335762a652255e1002b76c3b37937b4a4d8125d29d1501691fd3f418a8cef14",
  "url": "https://osv.dev/vulnerability/CVE-2026-63828",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "apparmor: mediate the implicit connect of TCP fast open sendmsg",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: apparmor: mediate the implicit connect of TCP fast open sendmsg sendmsg()/sendto() with MSG_FASTOPEN is a combination of connect(2) and write(2): it opens the connection in the SYN. apparmor_socket_sendmsg() only checks AA_MAY_SEND, so a profile that grants send but denies connect lets a confined task open an outbound TCP/MPTCP connection that connect(2) would have refused, bypassing connect mediation. Mediate the implicit connect when MSG_FASTOPEN is set and a destination is supplied. Add it to apparmor_socket_sendmsg() (not the shared aa_sock_msg_perm() helper, which recvmsg also uses) and call aa_sk_perm() directly, mirroring the selinux and tomoyo fixes. sk_is_tcp() does not cover MPTCP fast open, so the SOCK_STREAM/IPPROTO_MPTCP arm is explicit.",
    "evidence": "osv:CVE-2026-63828",
    "products": [
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        "name": {
          "value": "Kernel",
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        "prerequisites": [],
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    "severity": "high",
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      "id": "CVE-2026-63828",
      "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:C/C:H/I:H/A:N"
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      "modified": "2026-10-28T02:30:25.530855247Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/07b71c342382b854ab8030b244aeab6a7228ad7d",
        "https://git.kernel.org/stable/c/20383429b56974507c465d016e5238b189f7a246",
        "https://git.kernel.org/stable/c/45ebb934ea50b436ce49b2f159f090dab0d7fa28",
        "https://git.kernel.org/stable/c/4a69b83045d3195d5b9a9b053ad840ddb2998b4e",
        "https://git.kernel.org/stable/c/4d587cd8a72155089a627130bbd4716ec0856e21",
        "https://git.kernel.org/stable/c/7f57428ce00891d26b0f087ef754a4d820ec83aa",
        "https://git.kernel.org/stable/c/a16714e7cf2baa98ba2efddd5d6cbac641f4e76b",
        "https://git.kernel.org/stable/c/faea60deaa05c76f0772650f42eafde12bd39d93",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63828.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-63828",
        "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/2026/63xxx/CVE-2026-63828.json"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
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  "source_id": "core-osv",
  "document_id": 491727,
  "published_at": "2026-07-19T12:02:22.644+00:00"
}