tipc: fix use-after-free of the discoverer in tipc_disc_rcv()

{
  "id": "5d8aee38003758e6a43a236a9b0d1c8b4853f5b7e636281aea6ab664272cdcda",
  "url": "https://osv.dev/vulnerability/CVE-2026-64543",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "tipc: fix use-after-free of the discoverer in tipc_disc_rcv()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: tipc: fix use-after-free of the discoverer in tipc_disc_rcv() bearer_disable() frees b->disc with tipc_disc_delete()'s plain kfree(), but tipc_disc_rcv() still dereferences b->disc in RX softirq under rcu_read_lock() (tipc_udp_recv -> tipc_rcv -> tipc_disc_rcv). L2 bearers are safe thanks to the synchronize_net() in tipc_disable_l2_media(), but the UDP bearer defers that call to the cleanup_bearer() workqueue, so the discoverer is freed with no grace period: BUG: KASAN: slab-use-after-free in tipc_disc_rcv (net/tipc/discover.c:149) Read of size 8 at addr ffff88802348b728 by task poc_tipc/184 tipc_disc_rcv (net/tipc/discover.c:149) tipc_rcv (net/tipc/node.c:2126) tipc_udp_recv (net/tipc/udp_media.c:391) udp_rcv (net/ipv4/udp.c:2643) ip_local_deliver_finish (net/ipv4/ip_input.c:241) Freed by task 181: kfree (mm/slub.c:6565) bearer_disable (net/tipc/bearer.c:418) tipc_nl_bearer_disable (net/tipc/bearer.c:1001) The bearer is freed with kfree_rcu(); free the discoverer the same way. Add an rcu_head to struct tipc_discoverer and free it and its skb from an RCU callback. Because the RCU callback (tipc_disc_free_rcu) lives in module text, a call_rcu() that is still pending when the tipc module is unloaded would invoke a freed function. Add an rcu_barrier() to tipc_exit() after the bearer subsystem has been torn down, so all pending discoverer callbacks have run before the module text goes away. Reachable from an unpr",
    "evidence": "osv:CVE-2026-64543",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.265",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.216",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.183",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.145",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.97",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.40",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.5",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-64543",
      "aliases": [
        "CVE-2026-64543"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
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              "type": "GIT",
              "events": [
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                {
                  "fixed": "f05b3f4c78370469286879c765f5a1dd39dbcd32"
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                {
                  "fixed": "4da2ac7749411971e1b222b992da5a172ce45f98"
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                  "fixed": "5e215bf1c47fdddf8203a0fe80a0ed594065f101"
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            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64543.json"
          }
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        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
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                  "introduced": "4.17.0"
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            {
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64543.json"
          }
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      ],
      "modified": "2026-10-28T02:30:49.376349066Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1579342d71133da7f00daa02c75cebec7372097b",
        "https://git.kernel.org/stable/c/380413cdfd29fb9fa486c82889132b680c4983c5",
        "https://git.kernel.org/stable/c/4da2ac7749411971e1b222b992da5a172ce45f98",
        "https://git.kernel.org/stable/c/5e215bf1c47fdddf8203a0fe80a0ed594065f101",
        "https://git.kernel.org/stable/c/a0c5fdeb5fa257f8c6d469af266bc087cb5de6a2",
        "https://git.kernel.org/stable/c/b65289e1c3f352a9f92c6e19713ddd647e033253",
        "https://git.kernel.org/stable/c/ec7d54d8cc1723921d671e3272b427c96366506f",
        "https://git.kernel.org/stable/c/f05b3f4c78370469286879c765f5a1dd39dbcd32",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64543.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64543",
        "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/2026/64xxx/CVE-2026-64543.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-64543",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 518002,
  "published_at": "2026-07-27T20:10:35.565+00:00"
}