[CVE-2026-68189][MODERATE REGULAR] Bluetooth: hci_sync: Protect UUID list traversal

[CVE-2026-68189][MODERATE REGULAR] Bluetooth: hci_sync: Protect UUID list traversal

[AL-KERNEL]

CVE: CVE-2026-68189
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: hci_sync: Protect UUID list traversal
Commit: e4fa2c5c261d736b8e58759fdef3a968d510630c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e4fa2c5c261d736b8e58759fdef3a968d510630c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68189
Analysis date: Mon, 10 Aug 2026 16:01:04 -0400
ActionableScore: 4
ActionableScore lower bound: 2
Actionable bucket: Borderline Actionable Moderate candidate / Manual check required
Manual review required: YES

Summary:
A race in Bluetooth hci_sync allows asynchronous EIR or class of device generation to read a UUID entry after it was removed and freed through a local management socket, causing a confirmed kernel use after free with realistic DoS impact and limited but unproven escalation concern.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-68189 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68189

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-68189	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:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race in Bluetooth hci_sync can allow asynchronous EIR or class-of-device generation to traverse the UUID list while a management socket removes and frees a UUID entry. The worker may then read fields from the freed UUID object, producing a kernel use-after-free in eir_create and potentially crashing the system. For the CVSS the PR:L is used for the paranoid score because a local process with delegated Bluetooth management capability or CAP_NET_ADMIN may trigger UUID add/remove operations without full system administrator privileges. The issue is not directly network reachable because the triggering operations are local Bluetooth management commands, not remote Bluetooth traffic. Impact is at least local denial of service via kernel crash. In the worst still defensible case it may allow limited confidentiality or integrity impact due to stale freed object reads and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Actionable Moderate candidate / Manual check required (with actual score 3)	YES	REMOTE READ DANGER UAF NETWORK HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 4
* Final recommended bucket: **Borderline Actionable Moderate candidate / Manual check required**

## 2. Signal breakdown

Triggered signals:

* Memory corruption, weak primitive: +1
  Confirmed slab use after free in `eir_create()`, but the shown access is a stale read of `uuid->size`, with no demonstrated reclaim, overwrite, callback control, or type confusion.

* Real lifetime corruption: +1
  The bug is a real object lifetime race: `remove_uuid()` does `list_del()` and `kfree(uuid)` while async HCI sync work can still traverse the UUID list.

* Reliable kernel crash / strong DoS: +1
  KASAN reports a slab use after free in a kernel worker. A production kernel can plausibly Oops or panic depending on configuration.

* Broad/common subsystem exposure: +1
  Bluetooth is a commonly enabled kernel subsystem on endpoint systems, though not always enabled or relevant on servers.

Negative or limiting signals:

* Requires CAP_NET_ADMIN or Bluetooth management privilege in typical deployments: -2 for conservative score
  The add/remove UUID path is reached through Bluetooth management socket operations, which are normally privileged.

* Race/timing dependency limits exploitability
  This is a concurrent worker versus management command race. It is more than a pure validation bug, but no reliable attacker controlled reclaim path is shown.

Paranoid interpretation:

* The full privilege penalty is not applied in the paranoid score because delegated Bluetooth management capability, service accounts, containers, or reduced capability root can make the practical attacker weaker than full host root.
* No privilege escalation bonus is awarded. The patch shows UAF read and crash potential, but not controlled reuse, write after free, callback dispatch, refcount takeover, or arbitrary write.

## 3. Reachability analysis

A local process that can issue Bluetooth management commands can trigger the add/remove UUID side while async `hci_cmd_sync_work` generates EIR or class of device data. In normal deployments this usually requires CAP_NET_ADMIN or an equivalent Bluetooth management privilege, so the conservative view treats it as privileged local. In a more paranoid product triage view, Bluetooth management may be delegated to a service, container, or reduced capability account, so the effective privilege boundary can be weaker than full root.

The issue is not directly network reachable. The trigger is local management socket activity, not a remote Bluetooth packet. Bluetooth hardware and an active HCI device are likely required, so exposure is higher on desktops, laptops, and Bluetooth enabled appliances than on minimal servers.

Call-site confidence: high. The commit provides the interleaving, allocation and free stack traces, KASAN UAF report, and the exact locking fix around the list traversal.

## 4. Severity interpretation

This behaves like a confirmed local race based UAF with realistic DoS impact. It does not currently rise to a strong Important candidate because the demonstrated primitive is a stale read from a freed UUID object, not a controlled UAF reclaim, write primitive, function pointer overwrite, type confusion, or refcount takeover.

Theoretical memory corruption concern exists because this is a real kernel UAF in Bluetooth code. Realistic exploitation evidence points mainly to local kernel crash. Therefore it should not be auto closed as a trivial Moderate, but it also should not be treated as high confidence LPE without additional evidence.

## 5. One-sentence report phrase

A race in Bluetooth hci_sync allows asynchronous EIR or class of device generation to read a UUID entry after it was removed and freed through a local management socket, causing a confirmed kernel use after free with realistic DoS impact and limited but unproven escalation concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: confirmed kernel use after free in a commonly deployed subsystem, with local privileged or delegated management reachability. The current evidence supports DoS more strongly than LPE, but the lifetime bug class warrants manual review rather than automatic closure.

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

Patch: Bluetooth: hci_sync: Protect UUID list traversal
Commit: e4fa2c5c261d736b8e58759fdef3a968d510630c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e4fa2c5c261d736b8e58759fdef3a968d510630c

Commit description:

The hci_sync conversion moved class-of-device and EIR generation from an
HCI request built under hdev->lock to asynchronous command sync work.
The worker holds hdev->req_lock, but that lock does not serialize access
to hdev->uuids against add_uuid() and remove_uuid(), which update the
list under hdev->lock.

The following interleaving can therefore occur:

  CPU0 (command sync work)       CPU1 (management socket)
  fetch uuid from the list
                                list_del(&uuid->list)
                                kfree(uuid)
  read uuid->size

KASAN reports the resulting use-after-free:

  BUG: KASAN: slab-use-after-free in eir_create+0xb8f/0xee0
  Read of size 1 at addr ffff88810dbd8620 by task kworker/u17:0/87
  Workqueue: hci0 hci_cmd_sync_work
  Call Trace:
   eir_create+0xb8f/0xee0
   hci_update_eir_sync+0x1c0/0x330
   hci_cmd_sync_work+0x13c/0x290
   process_one_work+0x63a/0x1070
   worker_thread+0x45b/0xd10

  Allocated by task 86:
   __kasan_kmalloc+0x8f/0xa0
   add_uuid+0x18a/0x4b0
   hci_sock_sendmsg+0x1033/0x1ea0

  Freed by task 92:
   __kasan_slab_free+0x43/0x70
   kfree+0x131/0x3c0
   remove_uuid+0x25e/0x560
   hci_sock_sendmsg+0x1033/0x1ea0

Hold hdev->lock while generating and committing the class-of-device and
EIR snapshots.  Release it before sending an HCI command, so controller
waits do not happen under the device lock.  This protects all UUID list
walks in these paths and restores the serialization lost in the command
sync conversion.

Fixes: 161510c ("Bluetooth: hci_sync: Make use of hci_cmd_sync_queue set 1")
Cc: stable@vger.kernel.org
Signed-off-by: Chengfeng Ye <nicoyip.dev@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/bluetooth/hci_sync.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=e4fa2c5c261d736b8e58759fdef3a968d510630c

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

The original Linux kernel CVE announcement for CVE-2026-68189 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68189

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:H/UI:N/S:U/C:N/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: 2
  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).