[CVE-2026-68391][MODERATE 7.0] Bluetooth: mgmt: hold reference for hci_conn in mgmt_pending_cmds [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-68391
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: Bluetooth: mgmt: hold reference for hci_conn in mgmt_pending_cmds [ Upstream
Commit: b56f2ecafc08f372bf0529f9c4f3f429cb1702dc
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b56f2ecafc08f372bf0529f9c4f3f429cb1702dc
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68391
Analysis date: Mon, 10 Aug 2026 09:23:16 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
Bluetooth MGMT may store a stale hci_conn pointer in a pending command without holding a reference, allowing a race with connection teardown to cause a use after free in an hci_sync completion callback and potentially crash the kernel.

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

The original Linux kernel CVE announcement for CVE-2026-68391 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68391

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 7.0
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-2026-68391	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'Bluetooth MGMT can keep a stale hci_conn pointer in a pending command because the connection object is looked up and stored without holding a reference for the full async command lifetime. If the Bluetooth connection is removed before the hci_sync completion callback runs, the callback may dereference freed hci_conn memory and trigger a kernel use after free. For the CVSS the PR:L is used because a local process with access to the Bluetooth management control path is needed for reliable triggering, even though some deployments may restrict this path with network administration capability. The issue is not directly reachable over TCP/IP network traffic. A nearby Bluetooth peer may help create timing changes by connecting or disconnecting, but the vulnerable control operation is local. Impact is at least local denial of service via kernel crash. In the paranoid case this should be treated as a kernel UAF candidate that may allow confidentiality or integrity impact and possible privilege escalation if object reuse can be controlled.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE RACE UAF NETWORK KPANIC  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

* Memory corruption, weak primitive: +1
  The patch and commit message explicitly describe a possible UAF involving hci_conn, but the shown primitive is a race dependent stale pointer dereference, not a demonstrated controlled reclaim, overwrite, or type confusion.

* Real lifetime corruption: +1
  The fix adds hci_conn_get() when storing hci_conn in mgmt_pending_cmd and hci_conn_put() in completion callbacks, which directly confirms a refcount lifetime bug across asynchronous hci_sync callbacks.

* Reliable kernel crash / strong DoS: +1
  Dereferencing a freed hci_conn from a completion callback can realistically crash the kernel.

* External Bluetooth peer influence, not full remote network reachability: +1
  The vulnerable management command path is local, but Bluetooth connection lifetime and disconnect timing can be influenced by a nearby peer. This is weaker than AV:N network reachability and should not receive the full remote +2.

* Broad/default/common subsystem: +1
  Bluetooth is a common kernel subsystem on laptops, desktops, and some embedded devices, though not universally enabled on servers.

* Hard or unreliable race / special timing required: -1
  Exploitation depends on a timing window between a queued MGMT command, hci_conn lifetime changes, and asynchronous callback execution.

* Weak LPE concern in paranoid score: +1
  For the paranoid score, the stale hci_conn pointer survives into an async callback and may become exploitable if object reuse can be influenced. No concrete reclaim or write primitive is shown, so this is not strong LPE plausibility.

## 3. Reachability analysis

The direct trigger is local access to the Bluetooth MGMT control path. In many deployments this path is restricted to privileged components such as bluetoothd or processes with network administration capabilities, so it is not a normal unauthenticated remote attack surface. However, it is not equivalent to arbitrary host root in all threat models, because reduced capability services, containerized service contexts, or local policy mistakes may expose practical access.

A nearby Bluetooth peer cannot directly issue the MGMT command, but it may help create connection or disconnection timing needed for the race. The issue is not TCP/IP network reachable. Realistic exploitation requires Bluetooth support enabled, an active or recently active connection, and a local process able to issue the affected MGMT operations.

Call-site confidence: high. The patch includes the lookup, storage in cmd->user_data, async completion callbacks, and the added get/put lifetime handling.

## 4. Severity interpretation

This is more than an ordinary Moderate because it is a kernel lifetime bug with explicit UAF language and an async callback lifetime mismatch. The conservative interpretation is local DoS with a race dependent stale pointer dereference. The paranoid interpretation is Actionable Moderate because UAF in a kernel object lifetime path can sometimes be developed beyond DoS, but the patch does not show controlled reclaim, arbitrary write, type confusion, or function pointer control.

This should not be classified as Important solely from the diff. It should also not be auto-closed as a low-risk crash because the affected bug class is UAF/refcount lifetime corruption.

## 5. One-sentence report phrase

Bluetooth MGMT may store a stale hci_conn pointer in a pending command without holding a reference, allowing a race with connection teardown to cause a use after free in an hci_sync completion callback and potentially crash the kernel.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit UAF risk, async callback lifetime mismatch, and race dependent object lifetime corruption. The currently visible impact is DoS, but the bug class is suitable for manual review to assess reclaim control and possible LPE potential.

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

Patch: Bluetooth: mgmt: hold reference for hci_conn in mgmt_pending_cmds [ Upstream
Commit: b56f2ecafc08f372bf0529f9c4f3f429cb1702dc
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b56f2ecafc08f372bf0529f9c4f3f429cb1702dc

Changed files:
  net/bluetooth/mgmt.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=b56f2ecafc08f372bf0529f9c4f3f429cb1702dc

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

The original Linux kernel CVE announcement for CVE-2026-68391 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68391

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:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

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: 4
  Paranoid ActionableScore: 5

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: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).