CVE-2026-63944 (GCVE-0-2026-63944)
Vulnerability from cvelistv5
Published
2026-07-19 14:55
Modified
2026-08-05 12:37
Severity ?
8.8 (High) - CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_sync: fix UAF in hci_le_create_cis_sync hci_le_create_cis_sync() dereferences conn->conn_timeout after releasing both rcu_read_lock() and hci_dev_lock(hdev). The conn pointer was obtained from an RCU-protected iteration over hdev->conn_hash.list and is not valid once these locks are dropped. A concurrent disconnect can free the hci_conn between the unlock and the dereference, causing a use-after-free read. The cancellation mechanism in hci_conn_del() cannot prevent this because hci_le_create_cis_pending() queues hci_create_cis_sync with data=NULL: hci_cmd_sync_queue(hdev, hci_create_cis_sync, NULL, NULL); While hci_conn_del() dequeues with data=conn: hci_cmd_sync_dequeue(hdev, NULL, conn, NULL); Since NULL != conn, the lookup in _hci_cmd_sync_lookup_entry() never matches, and the pending work item is not cancelled. Fix this by saving conn->conn_timeout into a local variable while the locks are still held, so the stale conn pointer is never dereferenced after unlock. This is the same class of bug as the one fixed by commit 035c25007c9e ("Bluetooth: hci_sync: Fix UAF on le_read_features_complete") which addressed the identical pattern in a different function. This vulnerability was identified using 0sec.ai, an open-source automated security auditing platform (https://github.com/0sec-labs).
References
Impacted products
Vendor Product Version
Linux Linux Version: c09b80be6ffc338634b2f5f8cfa12b6843410834
Version: c09b80be6ffc338634b2f5f8cfa12b6843410834
Version: c09b80be6ffc338634b2f5f8cfa12b6843410834
Version: c09b80be6ffc338634b2f5f8cfa12b6843410834
Version: c09b80be6ffc338634b2f5f8cfa12b6843410834
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/bluetooth/hci_sync.c"
          ],
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          "product": "Linux",
          "programFiles": [
            "net/bluetooth/hci_sync.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "6.4"
            },
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              "status": "unaffected",
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              "version": "6.6.143",
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              "status": "unaffected",
              "version": "6.12.93",
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            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.35",
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            },
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              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.12",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.143",
                  "versionStartIncluding": "6.4",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.93",
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: hci_sync: fix UAF in hci_le_create_cis_sync\n\nhci_le_create_cis_sync() dereferences conn-\u003econn_timeout after releasing\nboth rcu_read_lock() and hci_dev_lock(hdev).  The conn pointer was\nobtained from an RCU-protected iteration over hdev-\u003econn_hash.list and\nis not valid once these locks are dropped.  A concurrent disconnect can\nfree the hci_conn between the unlock and the dereference, causing a\nuse-after-free read.\n\nThe cancellation mechanism in hci_conn_del() cannot prevent this because\nhci_le_create_cis_pending() queues hci_create_cis_sync with data=NULL:\n\n    hci_cmd_sync_queue(hdev, hci_create_cis_sync, NULL, NULL);\n\nWhile hci_conn_del() dequeues with data=conn:\n\n    hci_cmd_sync_dequeue(hdev, NULL, conn, NULL);\n\nSince NULL != conn, the lookup in _hci_cmd_sync_lookup_entry() never\nmatches, and the pending work item is not cancelled.\n\nFix this by saving conn-\u003econn_timeout into a local variable while the\nlocks are still held, so the stale conn pointer is never dereferenced\nafter unlock.\n\nThis is the same class of bug as the one fixed by commit 035c25007c9e\n(\"Bluetooth: hci_sync: Fix UAF on le_read_features_complete\") which\naddressed the identical pattern in a different function.\n\nThis vulnerability was identified using 0sec.ai, an open-source\nautomated security auditing platform (https://github.com/0sec-labs)."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:A - The bug is in the Bluetooth HCI ISO/CIS path (`hci_le_create_cis_sync`), reachable only via the Bluetooth radio interface. Per kernel CVSS guidance, Bluetooth vulnerabilities are scored as Adjacent, including on phones and LE Audio devices in public spaces.\nAC:L - The UAF is a race between `hci_le_create_cis_sync` dropping locks and a concurrent `hci_conn_del`. An attacker who controls one side of the CIS setup (local ISO socket threads or a remote peer timing ACL/CIS teardown) can repeatedly trigger the race; success does not depend on uncontrollable conditions like kernel memory layout.\nPR:N - No local Unix privileges are required for the highest-impact scenario: a remote Bluetooth peer in range can provoke CIS teardown/disconnect events while the victim host is performing normal LE Audio CIS establishment (e.g., phone connecting to earbuds). Local exploitation via ISO sockets also requires no special capabilities at the kernel level.\nUI:N - Both sides of the race run inside the kernel\u0027s own HCI event handling: hci_le_create_cis_pending() queues the vulnerable work from hci_le_cis_established_evt(), hci_cs_le_create_cis(), hci_unbound_cis_failed() and iso_connect_cfm(), all driven by controller events and remote peer traffic, while the freeing side is a peer-initiated disconnect reaching hci_conn_del(). On an LE Audio host the CIS establishment happens by itself when the earbuds connect and the attacker supplies the disconnect, so nothing is asked of the person holding the device; the existing pairing is a precondition of the deployment, not an in-attack user step.\nS:U - Impact is confined to kernel memory corruption within the Bluetooth subsystem on the host; this is standard kernel compromise, not a cross-boundary escape (KVM guest-to-host, IOMMU bypass, or sandbox breakout).\nC:H - This is a slab use-after-free read of `conn-\u003econn_timeout` on a freed `hci_conn` (kmalloc-8k object). UAF reads against attacker-influencable freed objects can disclose kernel heap contents and are scored as High per kernel CVSS guidance.\nI:H - Although the immediate bug is a post-unlock dereference of a freed `hci_conn`, UAF on large `hci_conn` kmalloc objects enables heap grooming and control of freed memory contents, which can be chained into arbitrary kernel writes or code execution; UAF class bugs are scored I:H.\nA:H - Use-after-free access to a freed connection object can cause kernel oops/panic (as demonstrated by the same bug class in the related `le_read_features_complete` fix found by syzkaller). Even without full exploitation, triggering the UAF reliably causes High availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:37:30.950Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a55618c0f4cead9e59c63f5ee030d393fd70d861"
        },
        {
          "url": "https://git.kernel.org/stable/c/a921957d39290143629eb38c4f74b9bef8035d0a"
        },
        {
          "url": "https://git.kernel.org/stable/c/d9019210c8c30d40eb20094274cc647e352f48f7"
        },
        {
          "url": "https://git.kernel.org/stable/c/380e67b1794a9a281a0cb592b4e62077fbd0c8ca"
        },
        {
          "url": "https://git.kernel.org/stable/c/bfea6091e0fffb270c20e74384b660910277eb6c"
        }
      ],
      "title": "Bluetooth: hci_sync: fix UAF in hci_le_create_cis_sync",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63944",
    "datePublished": "2026-07-19T14:55:39.105Z",
    "dateReserved": "2026-07-19T07:54:57.022Z",
    "dateUpdated": "2026-08-05T12:37:30.950Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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