[CVE-2026-53252][LOW] Bluetooth: fix memory leak in error path of hci_alloc_dev() [ Upstream

[CVE-2026-53252][LOW] Bluetooth: fix memory leak in error path of hci_alloc_dev() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53252
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: Bluetooth: fix memory leak in error path of hci_alloc_dev() [ Upstream
Commit: 5b7dfca6f852e6b9d809fd0263b5427cc9fb33fd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5b7dfca6f852e6b9d809fd0263b5427cc9fb33fd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53252
Analysis date: Thu, 25 Jun 2026 10:18:07 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A Bluetooth HCI initialization error path can leak SRCU percpu memory when an unregistered HCI device is released, allowing only local resource-exhaustion DoS if the failure path can be triggered repeatedly.

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

The original Linux kernel CVE announcement for CVE-2026-53252 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53252

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: LOW
Manual review required: NO

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

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

CVE-2026-53252	LOW	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A memory leak in the Bluetooth HCI device release path can occur when hci_alloc_dev initializes SRCU and device initialization fails before hci_register_dev completes. In that case HCI_UNREGISTER is not set, bt_host_release takes the unregistered fallback path, and the SRCU per CPU allocation is not cleaned up before kfree(hdev). For the CVSS the PR:L is used for the paranoid score because a reduced capability local actor with access to Bluetooth HCI UART setup or a delegated device management path may be able to repeat failed initialization attempts, while normal deployments usually restrict this to administrative users. The issue is not network reachable and does not provide a memory corruption primitive. Impact is denial of service only through gradual per CPU memory exhaustion if the failure path can be triggered repeatedly.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	REMOTE INIT LEAK ERRORPATH UAF NETWORK HARDWARE SYZBOT  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Availability impact realistic: +1. Repeated failed HCI device initialization can leak SRCU percpu memory and may eventually contribute to resource exhaustion.
* Requires admin/root/CAP style device management in typical deployments: -2. Triggering HCI UART configuration and failed HCI device setup is normally restricted to privileged local users or system services.
* Rare or difficult-to-reach configuration path: -1. The affected path is Bluetooth HCI UART initialization error handling, not a broad default packet-processing path.

Conservative total is floored at 0.

Paranoid signals:

* Local reduced-privilege or delegated device-management trigger: +1. A container, service, or reduced-capability local actor with delegated Bluetooth or device setup control might be able to repeat the failing path.
* Reliable resource-exhaustion DoS concern: +1. If the failure path is repeatable, leaked percpu SRCU allocations can accumulate.
* No memory corruption bonus. The patch fixes missing cleanup_srcu_struct before kfree(hdev), and does not show UAF, OOB write, double free, type confusion, callback misuse, or attacker-controlled reuse.
* No confidentiality or integrity bonus. The primitive is a resource leak only.

## 3. Reachability analysis

The bug is locally reachable through Bluetooth HCI device setup failure paths, especially HCI UART initialization before hci_register_dev completes. In normal deployments, this requires administrative control over Bluetooth device configuration or a privileged service managing HCI devices. It is not network reachable. Namespaces or containers may reduce the practical privilege requirement only if Bluetooth or device-management operations are explicitly delegated, but this is not the default exposure. Exploitation requires repeated triggering to turn a limited percpu memory leak into meaningful system pressure.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like resource leak, not an Important-class kernel vulnerability. The theoretical worst case is local denial of service through gradual memory exhaustion. There is no evidence of memory corruption, privilege escalation, sensitive data exposure, or cross-boundary policy bypass in the patch.

## 5. One-sentence report phrase

A Bluetooth HCI initialization error path can leak SRCU percpu memory when an unregistered HCI device is released, allowing only local resource-exhaustion DoS if the failure path can be triggered repeatedly.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a cleanup omission causing a bounded resource leak per failed initialization path, with no demonstrated corruption primitive or security-boundary bypass.

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

Patch: Bluetooth: fix memory leak in error path of hci_alloc_dev() [ Upstream
Commit: 5b7dfca6f852e6b9d809fd0263b5427cc9fb33fd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5b7dfca6f852e6b9d809fd0263b5427cc9fb33fd

Changed files:
  net/bluetooth/hci_sysfs.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=5b7dfca6f852e6b9d809fd0263b5427cc9fb33fd

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

The original Linux kernel CVE announcement for CVE-2026-53252 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53252

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:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 0
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).