CVE-2026-63944High· 8.8▾ Twilight

Bluetooth: hci_sync: fix UAF in hci_le_create_cis_sync

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(h…

▾ Twilight zone — High severity, or a signal on a lesser flaw

Depth score48/ 100 · Moderate

impact 48.4 · likelihood 0.1 · exploitation 0

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Proof of concept

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Published

Jul 19, 2026

Updated

Oct 19, 2026

CVSS

8.8

Vendor

Linux

Product

Linux

CWE

—

Depth score

48 · Moderate

EPSS

0.33% · p27

Platforms

—

Source

CVEORG

Vector

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA SSVC

decided 2026-10-16

Exploitation: none
Automatable: no
Technical impact: total

Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake. The CVSS score shown above comes from the assigning CNA record, not NVD.

EPSS history

Exploit-prediction probability, daily snapshots since Oct 16.

0.3% → 0.3%

Timeline

Disclosure to exploitation, from the record and what we observed since indexing it.

4 events · 99 days

Jul 19, 2026Published
Disclosed via CVEORG
Oct 16, 2026EPSS first tracked
0.3%
Oct 19, 2026Record revised
Last analysed / modified upstream
Oct 26, 2026EPSS peak
0.3% → 0.3%

Linux #cve.org

Affected

Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < a55618c0f4cead9e59c63f5ee030d393fd70d861
Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < a921957d39290143629eb38c4f74b9bef8035d0a
Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < d9019210c8c30d40eb20094274cc647e352f48f7
Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < 380e67b1794a9a281a0cb592b4e62077fbd0c8ca
Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < bfea6091e0fffb270c20e74384b660910277eb6c
Linux 6.4

Full technical detail▾

Overview

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).

Affected

Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < a55618c0f4cead9e59c63f5ee030d393fd70d861
Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < a921957d39290143629eb38c4f74b9bef8035d0a
Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < d9019210c8c30d40eb20094274cc647e352f48f7
Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < 380e67b1794a9a281a0cb592b4e62077fbd0c8ca
Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < bfea6091e0fffb270c20e74384b660910277eb6c
Linux 6.4

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

References

Related vulnerabilities

Connected by shared product, vendor, weakness, or advisory.

#cve.org

Bluetooth: hci_sync: fix UAF in hci_le_create_cis_sync

▾ Twilight zone — High severity, or a signal on a lesser flaw

Depth score48/ 100 · Moderate

impact 48.4 · likelihood 0.1 · exploitation 0

Overview

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: hci_sync: fix UAF in hci_le_create_cis_sync

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).

Affected

Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < a55618c0f4cead9e59c63f5ee030d393fd70d861

Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < a921957d39290143629eb38c4f74b9bef8035d0a

Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < d9019210c8c30d40eb20094274cc647e352f48f7

Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < 380e67b1794a9a281a0cb592b4e62077fbd0c8ca

Linux >= c09b80be6ffc338634b2f5f8cfa12b6843410834 < bfea6091e0fffb270c20e74384b660910277eb6c

Linux 6.4