[CVE-2026-64433][MODERATE REGULAR] Bluetooth: MGMT: Fix UAF of hci_conn_params in add_device_complete

[CVE-2026-64433][MODERATE REGULAR] Bluetooth: MGMT: Fix UAF of hci_conn_params in add_device_complete

[AL-KERNEL]

CVE: CVE-2026-64433
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: MGMT: Fix UAF of hci_conn_params in add_device_complete
Commit: caed4a96d55757c139a899744657c032b6186665
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=caed4a96d55757c139a899744657c032b6186665
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64433
Analysis date: Sat, 25 Jul 2026 07:56:19 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline manual review recommended / Actionable Moderate candidate
Manual review required: YES

Summary:
A race in Bluetooth MGMT allows `add_device_complete()` to read `hci_conn_params->flags` after a concurrent `MGMT_OP_REMOVE_DEVICE` frees the object, causing a local race-dependent UAF with realistic kernel crash impact but no demonstrated strong privilege-escalation primitive.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-64433 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64433

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: MODERATE REGULAR
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-64433	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race in Bluetooth MGMT can cause a use-after-free read of hci_conn_params in add_device_complete. The worker calls hci_conn_params_lookup and later reads params flags without holding hci_dev_lock, while a concurrent MGMT_OP_REMOVE_DEVICE path can free the same object. For the CVSS the PR:L is used because reliable triggering requires local access to the Bluetooth management interface such as a process with CAP_NET_ADMIN or equivalent delegated control, but not full kernel or host administrator privileges in all deployments. The issue is not directly network reachable because it is triggered through local MGMT control operations rather than remote Bluetooth traffic alone. Impact is at least local denial of service via kernel crash. The stale one byte flags read may also create limited confidentiality impact, and in the paranoid view limited integrity impact, but the patch context does not support an arbitrary write or strong privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Actionable Moderate candidate (with actual score 4)	YES	REMOTE READ LOCK DANGER UAF NETWORK HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: **3**
* Paranoid score: **4**
* Final recommended bucket: **Borderline manual review recommended / Actionable Moderate candidate**::

## 2. Signal breakdown

Triggered signals:

* **Memory corruption, weak primitive: +1**
  Confirmed race-dependent UAF read of `hci_conn_params->flags`, but only a 1-byte stale read is shown. No write-after-free, callback control, type confusion, or reclaim primitive is demonstrated.

* **Real lifetime corruption: +1**
  `remove_device()` can `list_del()` and `kfree()` the object after `hci_conn_params_lookup()` returns it, while `add_device_complete()` later dereferences it.

* **Reliable kernel crash / strong DoS: +1**
  KASAN reports slab-use-after-free in a kernel worker. On hardened/debug systems this is a clear crash path. On non-KASAN systems it may be less reliably fatal but still indicates unsafe lifetime handling.

* **Privileged kernel/device-management lifetime path: +1 paranoid only**
  This is Bluetooth MGMT device-control code managing HCI device state and connection parameters. The primitive is still weak, but the affected path is trusted kernel device-management state.

Negative signals:

* **Hard or unreliable race / special timing required: -1**
  The bug requires overlap between async `add_device_complete()` execution and concurrent `MGMT_OP_REMOVE_DEVICE`.

* **Requires CAP_NET_ADMIN or equivalent Bluetooth MGMT access in typical deployments: -1 conservative**
  Triggering normally requires local access to the Bluetooth management socket with administrative network/device-control privileges. This is not full host-root in all deployments, so I use `-1` rather than full `-2`.

Not awarded:

* No remote/network-triggerable bonus.
* No strong LPE bonus.
* No confidentiality/integrity bonus in the actionable score, because the patch shows stale read only and no demonstrated disclosure, controlled reclaim, object replacement, or write primitive.

## 3. Reachability analysis

The trigger is local through Bluetooth MGMT operations such as add/remove device. A realistic attacker needs access to the Bluetooth management interface, typically requiring `CAP_NET_ADMIN` or equivalent delegated control. Containers or service accounts with delegated Bluetooth or network administration may reduce the practical privilege barrier, but this is not reachable from remote Bluetooth traffic alone based on the patch. The path is relevant on systems with Bluetooth enabled and MGMT exposed to a local privileged or semi-privileged process.

Call-site confidence: **high**, because the provided commit message includes the exact lookup, dereference, freeing path, KASAN trace, and locking fix.

## 4. Severity interpretation

This behaves more like a **borderline / actionable Moderate** than a strong Important issue. The memory-lifetime bug is real and confirmed by KASAN, so it should not be auto-closed without review. However, the demonstrated primitive is a race-dependent 1-byte UAF read, not a write-after-free, callback dispatch, type confusion, refcount takeover, or attacker-controlled reclaim path. Realistic impact is local DoS, with only weak theoretical concern for stale-state effects.

## 5. One-sentence report phrase

A race in Bluetooth MGMT allows `add_device_complete()` to read `hci_conn_params->flags` after a concurrent `MGMT_OP_REMOVE_DEVICE` frees the object, causing a local race-dependent UAF with realistic kernel crash impact but no demonstrated strong privilege-escalation primitive.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED**

Reason: confirmed kernel UAF and race in Bluetooth MGMT lifetime handling. The primitive appears weak, but lifetime bugs in device-management code deserve manual review to confirm whether object reuse or stale flag influence can create impact beyond DoS.

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: Bluetooth: MGMT: Fix UAF of hci_conn_params in add_device_complete
Commit: caed4a96d55757c139a899744657c032b6186665
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=caed4a96d55757c139a899744657c032b6186665

Commit description:

add_device_complete() runs from the hci_cmd_sync_work kworker, which
holds only hci_req_sync_lock and *not* hci_dev_lock.  It calls
hci_conn_params_lookup() and then dereferences the returned object
(params->flags) without taking hci_dev_lock:

	params = hci_conn_params_lookup(hdev, &cp->addr.bdaddr,
					le_addr_type(cp->addr.type));
	...
	device_flags_changed(NULL, hdev, &cp->addr.bdaddr,
			     cp->addr.type, hdev->conn_flags,
			     params ? params->flags : 0);

hci_conn_params_lookup() walks hdev->le_conn_params and is documented to
require hdev->lock.  A concurrent MGMT_OP_REMOVE_DEVICE
(remove_device()), which does run under hci_dev_lock, can call
hci_conn_params_free() to list_del() and kfree() the very object the
lookup returned, so the subsequent params->flags read touches freed
memory [0].

Hold hci_dev_lock() across the hci_conn_params_lookup() and the read of
params->flags (and the matching event emission) so the lookup result
cannot be freed by a concurrent remove_device() before it is used,
honouring the locking contract of hci_conn_params_lookup().

[0]: (trailing page/memory-state dump trimmed)
BUG: KASAN: slab-use-after-free in add_device_complete+0x358/0x3d8 net/bluetooth/mgmt.c:7671
Read of size 1 at addr ffff000017ab26c1 by task kworker/u9:8/388

CPU: 1 UID: 0 PID: 388 Comm: kworker/u9:8 Not tainted 7.0.11 #20 PREEMPT
Hardware name: linux,dummy-virt (DT)
Workqueue: hci0 hci_cmd_sync_work
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0xb4/0xd4 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x118/0x5d8 mm/kasan/report.c:482
 kasan_report+0xb0/0xf4 mm/kasan/report.c:595
 __asan_report_load1_noabort+0x20/0x2c mm/kasan/report_generic.c:378
 add_device_complete+0x358/0x3d8 net/bluetooth/mgmt.c:7671
 hci_cmd_sync_work+0x14c/0x240 net/bluetooth/hci_sync.c:334
 process_one_work+0x628/0xd38 kernel/workqueue.c:3289
 process_scheduled_works kernel/workqueue.c:3372 [inline]
 worker_thread+0x7a8/0xac0 kernel/workqueue.c:3453
 kthread+0x39c/0x444 kernel/kthread.c:436
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860

Allocated by task 3401:
 kasan_save_stack+0x3c/0x64 mm/kasan/common.c:57
 kasan_save_track+0x20/0x3c mm/kasan/common.c:78
 kasan_save_alloc_info+0x40/0x54 mm/kasan/generic.c:570
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xd4/0xd8 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x1b0/0x458 mm/slub.c:5385
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 hci_conn_params_add+0x10c/0x4b0 net/bluetooth/hci_core.c:2279
 hci_conn_params_set net/bluetooth/mgmt.c:5162 [inline]
 add_device+0x5b4/0xa54 net/bluetooth/mgmt.c:7755
 hci_mgmt_cmd net/bluetooth/hci_sock.c:1721 [inline]
 hci_sock_sendmsg+0x10b4/0x1dd0 net/bluetooth/hci_sock.c:1841
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0xe0/0x128 net/socket.c:742
 sock_write_iter+0x250/0x390 net/socket.c:1195
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x66c/0xab0 fs/read_write.c:688
 ksys_write+0x1fc/0x24c fs/read_write.c:740
 __do_sys_write fs/read_write.c:751 [inline]
 __se_sys_write fs/read_write.c:748 [inline]
 __arm64_sys_write+0x70/0xa4 fs/read_write.c:748
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x84/0x2a8 arch/arm64/kernel/syscall.c:49
 el0_svc_common.constprop.0+0xe4/0x294 arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x44/0x5c arch/arm64/kernel/syscall.c:151
 el0_svc+0x38/0xac arch/arm64/kernel/entry-common.c:724
 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:743
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

Freed by task 3740:

[Commit description truncated; see the upstream URL below]

Changed files:
  net/bluetooth/mgmt.c
  arch/arm64/kernel/stacktrace.c
  lib/dump_stack.c
  mm/kasan/report.c
  mm/kasan/report_generic.c
  net/bluetooth/hci_sync.c
  kernel/workqueue.c
  kernel/kthread.c
  arch/arm64/kernel/entry.S
  mm/kasan/common.c
  mm/kasan/generic.c
  include/linux/kasan.h
  mm/slub.c
  include/linux/slab.h
  net/bluetooth/hci_core.c
  net/bluetooth/hci_sock.c
  net/socket.c
  fs/read_write.c
  arch/arm64/kernel/syscall.c
  arch/arm64/kernel/entry-common.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=caed4a96d55757c139a899744657c032b6186665

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-64433 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64433

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 3
  Paranoid ActionableScore: 4

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).