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Bluetooth: ISO: avoid NULL deref of conn in iso_conn_big_sync()

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: ISO: avoid NULL deref of conn in iso_conn_big_sync() iso_conn_big_sync() drops the socket lock to call hci_get_route() and then re-acquires it, but dereferences iso_pi(sk)->conn->hcon afterwards without re-checking that conn is still valid. While the lock is dropped, the connection can be torn down under the same socket lock: iso_disconn_cfm() -> iso_conn_del() -> iso_chan_del() sets iso_pi(sk)->conn to NULL (and the broadcast teardown path can also clear conn->hcon on its own). When iso_conn_big_sync() re-acquires the lock and reads conn->hcon, conn may be NULL, causing a NULL pointer dereference (hcon is the first member of struct iso_conn). This path is reached from iso_sock_recvmsg() for a PA-sync broadcast sink socket (BT_SK_DEFER_SETUP | BT_SK_PA_SYNC), so the dropped-lock window can race with connection teardown driven by controller events. Re-validate iso_pi(sk)->conn and its hcon after re-acquiring the socket lock and bail out if the connection went away, as already done in the sibling iso_sock_rebind_bc().

Products
Kernel
Affected versions
Not specified
Fixed versions
6.12.96, 6.18.39, 7.1.4
CVEs
CVE-2026-64404
Confirmed fixed CVEs
Not specified
Updated in this feed
7 Nov 2026, 18:34 UTC · Revision 1

Source evidence

Bluetooth: ISO: avoid NULL deref of conn in iso_conn_big_sync()

core-osv · Original source

Published 25 Jul 2026, 08:50 UTC

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: ISO: avoid NULL deref of conn in iso_conn_big_sync() iso_conn_big_sync() drops the socket lock to call hci_get_route() and then re-acquires it, but dereferences iso_pi(sk)->conn->hcon afterwards without re-checking that conn is still valid. While the lock is dropped, the connection can be torn down under the same socket lock: iso_disconn_cfm() -> iso_conn_del() -> iso_chan_del() sets iso_pi(sk)->conn to NULL (and the broadcast teardown path can also clear conn->hcon on its own). When iso_conn_big_sync() re-acquires the lock and reads conn->hcon, conn may be NULL, causing a NULL pointer dereference (hcon is the first member of struct iso_conn). This path is reached from iso_sock_recvmsg() for a PA-sync broadcast sink socket (BT_SK_DEFER_SETUP | BT_SK_PA_SYNC), so the dropped-lock window can race with connection teardown driven by controller events. Re-validate iso_pi(sk)->conn and its hcon after re-acquiring the socket lock and bail out if the connection went away, as already done in the sibling iso_sock_rebind_bc().

osv:CVE-2026-64404

Kernel

Fixed versions: 6.12.96, 6.18.39, 7.1.4

Complete source record
{
  "id": "9d1d4020dfd7a62fa836dbfb30275893ccbc47a29f246db956867f8dd87ef353",
  "url": "https://osv.dev/vulnerability/CVE-2026-64404",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Bluetooth: ISO: avoid NULL deref of conn in iso_conn_big_sync()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: Bluetooth: ISO: avoid NULL deref of conn in iso_conn_big_sync() iso_conn_big_sync() drops the socket lock to call hci_get_route() and then re-acquires it, but dereferences iso_pi(sk)->conn->hcon afterwards without re-checking that conn is still valid. While the lock is dropped, the connection can be torn down under the same socket lock: iso_disconn_cfm() -> iso_conn_del() -> iso_chan_del() sets iso_pi(sk)->conn to NULL (and the broadcast teardown path can also clear conn->hcon on its own). When iso_conn_big_sync() re-acquires the lock and reads conn->hcon, conn may be NULL, causing a NULL pointer dereference (hcon is the first member of struct iso_conn). This path is reached from iso_sock_recvmsg() for a PA-sync broadcast sink socket (BT_SK_DEFER_SETUP | BT_SK_PA_SYNC), so the dropped-lock window can race with connection teardown driven by controller events. Re-validate iso_pi(sk)->conn and its hcon after re-acquiring the socket lock and bail out if the connection went away, as already done in the sibling iso_sock_rebind_bc().",
    "evidence": "osv:CVE-2026-64404",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "value": "6.12.96",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.39",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
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      "aliases": [
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      "affected": [
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          "database_specific": {
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        },
        {
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                  "introduced": "0"
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              ]
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            {
              "type": "ECOSYSTEM",
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          ],
          "package": {
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            "ecosystem": "Linux"
          },
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          }
        }
      ],
      "modified": "2026-10-28T02:30:51.609740299Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/01afd198c2c286cd3b81f44d4e33a2e638711550",
        "https://git.kernel.org/stable/c/b3e647a4aa4d2d054f86a783f5c426035e1dc237",
        "https://git.kernel.org/stable/c/b84eeb7636d6962dd882d5e0b31475e4f404313c",
        "https://git.kernel.org/stable/c/d5541eb148da72d5e0a1bca8ecd171f9fc8b366f",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64404.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64404",
        "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-2026-64404.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-64404",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 520105,
  "published_at": "2026-07-25T08:50:46.523+00:00"
}