[CVE-2026-74538][MODERATE 7.0] Bluetooth: ISO: lock sk in iso_connect_ind [ Upstream

[CVE-2026-74538][MODERATE 7.0] Bluetooth: ISO: lock sk in iso_connect_ind [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74538
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: ISO: lock sk in iso_connect_ind [ Upstream
Commit: e8e9cff6d80eeec28dec4cf7cc18662986945391
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e8e9cff6d80eeec28dec4cf7cc18662986945391
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74538
Analysis date: Sat, 15 Aug 2026 16:10:01 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-74538 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74538

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-2026-74538	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:L/I:L/A:H';CWE-362;CWE-667;**CWE-476;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'A race in the Bluetooth/ISO connect indication path can access ISO socket private connection state without holding the socket lock. The ev3 path can read a stale or NULL connection pointer if the socket leaves LISTEN or CONNECT state while HCI event handling is in progress, which can lead to a NULL pointer dereference and kernel crash. Because the access is protected by lock_sock in adjacent paths, the missing lock indicates a real synchronization bug and a possible UAF candidate if the connection object is freed concurrently. For the CVSS the PR:N is used in the paranoid score because an adjacent Bluetooth attacker may trigger the HCI event stream without a local account when a vulnerable ISO listener is already present, although reliable exploitation likely depends on timing and local Bluetooth configuration. The issue is adjacent network reachable over Bluetooth rather than Internet reachable. Impact is at least denial of service and in worst case may allow limited confidentiality or integrity impact due to race based memory corruption risk.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	REMOTE LOCK SIMPLEFIX NETWORK  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

2. Signal breakdown
* +1 Local unprivileged trigger: a local process with access to Bluetooth ISO socket functionality may participate in the vulnerable state transition path.
* +1 Firmware-mediated external influence: the affected path is driven by Bluetooth HCI events and nearby radio/controller activity, but it is not Internet-reachable.
* +1 Memory corruption, weak/indirect corruption candidate: the unlocked access to iso_pi(sk)->conn can observe NULL or stale connection state, but no controlled reclaim, overwrite, callback control, or type confusion is shown.
* +1 Real lifetime corruption: the bug is a socket/connection lifetime synchronization issue, where state can transition away from LISTEN/CONNECT before the access is protected.
* +1 Reliable kernel crash / strong DoS: the direct demonstrated failure mode is NULL pointer dereference leading to kernel crash.
* -1 Hard or unreliable race / special timing required: exploitation depends on a socket state transition racing with HCI event handling.
* -1 Rare AND difficult-to-reach subsystem/configuration: Bluetooth ISO broadcast sink paths are not common default exposure on most systems.
* Paranoid-only +2 Adjacent network-triggerable: a nearby Bluetooth attacker may influence the HCI event stream if a vulnerable ISO listener is already configured.
* Paranoid-only +1 Confidentiality impact plausible and +1 Integrity impact plausible: only as a manual-review sensitivity signal for race-based stale pointer access. This is not a demonstrated LPE primitive.

3. Reachability analysis
The conservative trigger model is local: an attacker needs local access to create or influence the relevant Bluetooth ISO socket state, or to interact with a local Bluetooth service that exposes it. The paranoid model treats the issue as adjacent-network reachable over Bluetooth when an ISO listener or broadcast sink is already active. Containers usually do not improve reachability because Bluetooth devices and management are commonly host-controlled and not broadly namespaced. The affected path is not default Internet-facing and requires Bluetooth ISO support plus a suitable runtime configuration.

4. Severity interpretation
This behaves above ordinary Moderate because it is a real locking/lifetime bug in a network-adjacent kernel subsystem and can plausibly crash the kernel. It does not reach a Strong Important level conservatively because the patch only demonstrates NULL or stale pointer access, not attacker-controlled reclaim, write-after-free, type confusion, callback dispatch, or arbitrary memory corruption. The paranoid score is Actionable Moderate because adjacent Bluetooth influence plus lifetime-race semantics are enough to require manual review.

5. One-sentence report phrase
A race in Bluetooth ISO iso_connect_ind can access socket connection state without lock_sock, allowing NULL or stale connection state during HCI event handling and causing at least a kernel crash, with adjacent Bluetooth reachability possible when a vulnerable ISO listener is active.

6. Manual review recommendation
MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK because this is a Bluetooth adjacent race involving socket and connection lifetime, with a proven crash path and a weak but nonzero stale-pointer concern.

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

Patch: Bluetooth: ISO: lock sk in iso_connect_ind [ Upstream
Commit: e8e9cff6d80eeec28dec4cf7cc18662986945391
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e8e9cff6d80eeec28dec4cf7cc18662986945391

Changed files:
  net/bluetooth/iso.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=e8e9cff6d80eeec28dec4cf7cc18662986945391

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

The original Linux kernel CVE announcement for CVE-2026-74538 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74538

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:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.4

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: 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: NO
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).