[CVE-2026-90252][LOW] Bluetooth: MGMT: free the HCI command when it is cancelled [ Upstream

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

CVE: CVE-2026-90252
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: Bluetooth: MGMT: free the HCI command when it is cancelled [ Upstream
Commit: e0cd7b34dc6b5414cac3d4cd376f73d3e9ffbd93
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0cd7b34dc6b5414cac3d4cd376f73d3e9ffbd93
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90252
Analysis date: Fri, 18 Sep 2026 08:29:40 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
Bluetooth MGMT HCI command sync cancellation can leak a pending command object and pin its socket reference when the queued entry is cancelled before execution, causing resource leakage and possible local DoS under repeated cancellation scenarios.

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

The original Linux kernel CVE announcement for CVE-2026-90252 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90252

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-2026-90252	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90252 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: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: '4.7';DESCR 'Bluetooth MGMT command sync cancellation can leak a pending command object because mgmt_hci_cmd_sync() queued the command without a destroy callback. If the queued entry is cancelled before send_hci_cmd_sync() runs, for example during controller unregister, the entry data is not released and the socket reference taken by mgmt_pending_new() remains pinned. For the CVSS the PR:L is used for the paranoid score because delegated CAP_NET_ADMIN or a constrained local service account may be enough in some deployments, although full administrative control is typical for reliable triggering. The issue is not network reachable and is triggered through the local Bluetooth management control path rather than over the air Bluetooth traffic. Impact is denial of service only through memory and socket reference leakage under repeated cancellation scenarios.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	REMOTE INIT LEAK UAF NETWORK  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

## 1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1. No floor or cap applied.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::

## 2. Signal breakdown

Conservative signals:

* +1 Concrete persistent kernel resource/reference leak. The patch establishes that a pending MGMT command object is allocated and queued, but if the queued HCI command sync entry is cancelled before `send_hci_cmd_sync()` runs, the command is not freed.
* +0 Reliable kernel crash / strong DoS not awarded. The supplied evidence shows a memory leak and pinned socket reference, not an immediate kernel crash.
* +0 Local unprivileged trigger not awarded. The supplied patch does not establish ordinary unprivileged reachability to the complete trigger.
* +0 Remote/network trigger not awarded. This is a local Bluetooth MGMT control path issue, not over-the-air Bluetooth packet processing and not direct network reachability.
* +0 C/I not awarded. No information disclosure, unauthorized modification, UAF, OOB access, arbitrary write, or authorization bypass is established.

Paranoid additional signal:

* +1 Potential sustained resource exhaustion. Repeated cancellation scenarios could accumulate leaked pending command objects and pinned socket references, but this remains resource leakage only.

Important non-awarded signals:

* RealUAF not awarded. The bug is a missing cleanup callback and persistent leak, not a stale post-free use.
* Concrete repeated release/refcount not awarded. There is no first release that may end lifetime followed by a second lifetime mutation through the same dangling reference.
* Strong LPE or weak LPE not awarded. No memory corruption or security boundary primitive is visible.
* Structured stale-object leverage not awarded. No stale object is consumed after free.
* Extra Availability not awarded beyond paranoid resource exhaustion. No distinct host-wide fatal condition is demonstrated.
* ImportantCandidate not awarded because this is a leak-only CLASS_C issue without unresolved corruption leverage.

## 3. Reachability analysis

The reachable operation is `MGMT_OP_HCI_CMD_SYNC` through the Bluetooth MGMT control path. The leak occurs when a queued command is cancelled before `send_hci_cmd_sync()` executes, for example when `hci_cmd_sync_clear()` cancels pending entries during controller unregister.

The supplied context does not show the complete capability checks for issuing this MGMT command or for triggering controller unregister. In typical systems, Bluetooth management and controller unregister/reset operations are privileged or controlled by system services, but the prompt requires positive evidence for host-admin classification. Therefore `HostAdminRequired=UNKNOWN`.

The complete trigger is not shown to be namespace-scoped. Bluetooth MGMT controller management is not established here as attacker-obtainable through a created user or network namespace, so `NamespaceScopedPrivilege=NO`.

No prior remote attacker path is established. No special rare hardware requirement is scored, because the issue is in a normal Bluetooth subsystem path, but no broad/default exposure bonus is awarded either.

Race/timing penalty is not applied. The issue is not primarily a narrow race. It is an ordered cancellation cleanup path missing a destroy callback.

## 4. Primitive and severity interpretation

The exact primitive is a persistent resource/reference leak. `mgmt_hci_cmd_sync()` queues a `mgmt_pending` command with a NULL destroy callback. If the queued entry is cancelled instead of executed, `_hci_cmd_sync_cancel_entry()` does not release `entry->data`. Because `mgmt_pending_new()` also takes a socket reference, the leaked pending command pins the MGMT socket as well.

This is not active structured UAF and not fixed stale storage UAF. It is a missing release of an owned object and its associated socket reference.

Demonstrated consequence: memory/reference leak and possible resource exhaustion if repeated.

Speculative consequence: broader DoS through accumulated memory/socket references. No supported path to privilege escalation, kernel memory corruption, information disclosure, or arbitrary write is established.

Primitive class is `CLASS_C`: resource leak / DoS-style behavior without an independently useful corruption primitive.

`ImportantCandidate=NO` because no Class A primitive and no meaningful Class B lifetime-corruption leverage is present.

`AutoDowngradeAllowed=YES` because this is a constrained leak-only issue with no UAF, no repeated refcount mutation, no authorization bypass, and no demonstrated security-boundary consequence.

Likely operational severity is Low / ordinary Moderate depending on how easily a local privileged or service-level actor can repeat cancellation during controller unregister.

## 5. One-sentence report phrase

Bluetooth MGMT HCI command sync cancellation can leak a pending command object and pin its socket reference when the queued entry is cancelled before execution, causing resource leakage and possible local DoS under repeated cancellation scenarios.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the patch establishes a concrete resource/reference leak only. No UAF, double release, memory corruption, authorization bypass, network reachability, or privilege-escalation primitive is supported.

## 7. Call-site confidence

Call-site confidence: high

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

Patch: Bluetooth: MGMT: free the HCI command when it is cancelled [ Upstream
Commit: e0cd7b34dc6b5414cac3d4cd376f73d3e9ffbd93
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0cd7b34dc6b5414cac3d4cd376f73d3e9ffbd93

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=e0cd7b34dc6b5414cac3d4cd376f73d3e9ffbd93

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

The original Linux kernel CVE announcement for CVE-2026-90252 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90252

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:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 1
  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).