[CVE-2026-68393][MODERATE 7.0] Bluetooth: hci_sync: extend conn_hash lookup critical sections [ Upstream

[CVE-2026-68393][MODERATE 7.0] Bluetooth: hci_sync: extend conn_hash lookup critical sections [ Upstream

[AL-KERNEL]

CVE: CVE-2026-68393
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: Bluetooth: hci_sync: extend conn_hash lookup critical sections [ Upstream
Commit: 83b7e67698d0b93f685875ce82c8d335436834f7
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=83b7e67698d0b93f685875ce82c8d335436834f7
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68393
Analysis date: Mon, 10 Aug 2026 18:34:54 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
Bluetooth hci_sync may use RCU protected hci_conn pointers after the lookup critical section, allowing a nearby Bluetooth attacker under race conditions to potentially trigger a UAF and kernel DoS.

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

The original Linux kernel CVE announcement for CVE-2026-68393 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68393

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-2026-68393	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'Bluetooth hci_sync used RCU protected hci_conn pointers outside the lookup critical section and without a refcount, creating a possible use-after-free when a connection is deleted concurrently. An attacker in Bluetooth radio range may be able to influence connection lifetime while the host performs scan, advertising, address resolution, or accept list updates, making the issue adjacent network reachable rather than Internet reachable. For the CVSS the PR:N is used for the paranoid score because a nearby Bluetooth attacker may not need a local account on the victim if the vulnerable state machine is reachable through Bluetooth activity. AC:H is used because reliable triggering depends on a race window and specific controller and connection state. Impact is at least denial of service and in the worst defensible case may include confidentiality or integrity impact due to UAF based memory corruption, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE OOB LOCK UAF NETWORK HARDWARE KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

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

## 2. Signal breakdown

* Remote reachable / network-adjacent trigger: +2
  Bluetooth is not Internet reachable, but a nearby attacker may influence LE connection, scan, advertising, PA sync, or accept-list state over the radio interface.

* Memory corruption, weak primitive: +1
  The commit explicitly says RCU-protected pointers may be used outside the critical section and may result in UAF. However, the patch shows stale pointer dereference/lifetime exposure, not attacker-controlled reclaim, overwrite, callback control, or type confusion.

* Real lifetime corruption: +1
  This is an RCU lifetime bug involving hci_conn objects that may be deleted concurrently while still being dereferenced.

* Hard or unreliable race / special timing required: -1
  Triggering depends on a race between hci_conn lookup/use and concurrent connection deletion.

* Availability impact realistic: +1
  UAF dereference in the Bluetooth kernel path can plausibly crash the kernel or destabilize the Bluetooth stack.

Paranoid-only elevation:

* Manual-review UAF concern: +1
  The issue is an externally influenced RCU UAF in a wireless networking subsystem. Even without a demonstrated reclaim primitive, this should not be auto-closed.

Race-UAF cap applied:

* Conservative score capped at 4.
* Paranoid score capped at 5 because the patch does not show attacker-controlled reclaim, write-after-free, callback dispatch, type confusion, or refcount takeover.

## 3. Reachability analysis

A local user account is not necessarily required if the vulnerable state transitions can be influenced by a nearby Bluetooth peer. The realistic external attacker model is adjacent radio range, not Internet remote. The affected paths involve Bluetooth LE connection lookup, passive scan updates, address resolution, PA sync, and accept-list processing. Triggering likely requires Bluetooth hardware enabled, relevant LE activity, and precise timing against connection teardown.

Namespaces and containers do not substantially improve reachability unless they expose Bluetooth management or HCI access. In typical desktop or mobile-like deployments Bluetooth may be common, but on servers it is often absent or disabled.

Call-site confidence: high, because the patch shows multiple direct lookup and use sites in hci_sync.c and explicitly extends RCU critical sections around those uses.

## 4. Severity interpretation

This behaves stronger than an ordinary Moderate because it is an RCU lifetime bug with explicit UAF potential in a network-adjacent Bluetooth path. The realistic demonstrated impact is denial of service or kernel instability from stale hci_conn dereference. Theoretical confidentiality or integrity impact is possible only in a paranoid sense because UAF bugs can sometimes become stronger primitives, but this patch does not show controlled reclaim, writable stale access, function pointer control, or object confusion.

Therefore the practical classification is Actionable Moderate at minimum, with manual review required. It is not a strong Important candidate on the conservative evidence alone.

## 5. One-sentence report phrase

Bluetooth hci_sync may use RCU protected hci_conn pointers after the lookup critical section, allowing a nearby Bluetooth attacker under race conditions to potentially trigger a UAF and kernel DoS.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is an RCU race with explicit UAF potential and adjacent Bluetooth exposure. The current patch supports DoS more strongly than privilege escalation, but lifetime bugs in externally influenced networking paths should receive manual review rather than automatic closure.

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

Patch: Bluetooth: hci_sync: extend conn_hash lookup critical sections [ Upstream
Commit: 83b7e67698d0b93f685875ce82c8d335436834f7
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=83b7e67698d0b93f685875ce82c8d335436834f7

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=83b7e67698d0b93f685875ce82c8d335436834f7

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

The original Linux kernel CVE announcement for CVE-2026-68393 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68393

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:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.5

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).