[CVE-2026-99091][LOW] Bluetooth: MGMT: Fix status of pending commands flushed on power off

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

CVE: CVE-2026-99091
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: Bluetooth: MGMT: Fix status of pending commands flushed on power off
Commit: 44ce36c5789ac84e65de1e98c32db9a5ac04ed47
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=44ce36c5789ac84e65de1e98c32db9a5ac04ed47
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99091
Analysis date: Mon, 26 Oct 2026 22:40:29 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
Bluetooth MGMT could return a pointer-derived or false-success status for flushed pending commands, crashing affected older bluetoothd versions without corrupting kernel memory.

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

The original Linux kernel CVE announcement for CVE-2026-99091 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99091

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-99091	LOW	https://www.kernelcve.org/list/?q=CVE-2026-99091 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE AEGIS_AS=2 LEGACY=LOW RESULT=DIFF (final Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:L';CWE-843;CWE-704;CWE-682;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.6';DESCR 'A Bluetooth MGMT pending command lacking a cmd_complete callback was completed with a status read from the first byte of match sk instead of match mgmt_status. A NULL socket produced a false Success response, while a pending Set Powered command could produce a status byte derived from the socket pointer. The demonstrated consequence was a crash of bluetoothd 5.72 after Start Discovery received a zero length Success reply, although newer BlueZ versions validate the reply length. For the CVSS the PR:L value reflects the local permissions needed to request Bluetooth management operations through bluetoothd or another authorized control path. The trigger also requires a pending command to be flushed during power off or device removal, so AC:H is used. There is no kernel memory corruption primitive and the primary impact is limited Bluetooth service disruption. A one byte pointer derived disclosure is considered only in the paranoid vector because its practical confidentiality value is small and depends on the pending command state and architecture. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 3.6 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage IMPORTANT to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 5.4 and ActionableScore 2 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	MAYBE	REMOTE DANGER NETWORK HARDWARE LINUS LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1.
* Raw paranoid score: 2.
* Paranoid score: 2.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 service availability impact: the incorrect Success response with no parameters demonstrably crashed bluetoothd 5.72. This is userspace Bluetooth-service disruption, not a kernel crash.
* Paranoid +1 limited confidentiality: `cmd_status_rsp()` returns one byte taken from the representation of `match->sk` when non-NULL. This is an actual kernel-pointer-derived byte crossing to userspace, but its practical information value is small and architecture/alignment dependent.
* No kernel-memory write, UAF, OOB access, lifetime corruption, or active structured-state corruption is shown.
* No authorization decision changes from DENY to ALLOW; the fix selects the intended status field rather than restoring a security guard.
* No extra availability point: the same bluetoothd crash is not counted twice.
* No LPE, protected-resource access, arbitrary disclosure, kernel panic, or remote reachability is shown.
* NEW52 B5-R and NEW53 B3-PENDING do not apply: there is no write or shared-backing modification.

3. Reachability analysis

An authorized local Bluetooth-management client can create a pending command and arrange for it to be flushed during adapter power-off or removal. The supplied triage evidence characterizes this as low-privilege local access through bluetoothd or another authorized control path, so effective host-administrator power and host UID 0 are not required. Namespace-scoped capability reachability is not established. Triggering requires a specific pending-command/power-transition sequence, but this does not alter the low score.

4. Primitive and severity reading

The defect is a wrong-field interpretation: a `struct cmd_lookup *` is treated as a `u8 *`, causing an incorrect protocol status byte to be returned. It does not corrupt kernel state. The proven effect is a malformed management response and crash of an older userspace daemon; newer BlueZ validates the response length. The pointer-derived byte is a narrow disclosure concern only, with no shown sensitive follow-on use. Therefore `PrimitiveClass=NONE`, no Important candidate exists, and automatic downgrade is safe.

5. One-sentence report phrase

Bluetooth MGMT could return a pointer-derived or false-success status for flushed pending commands, crashing affected older bluetoothd versions without corrupting kernel memory.

6. Manual review advice

NO MANUAL CHECK NEEDED

The patch-supported effects are limited to incorrect status reporting, userspace service disruption, and at most a low-value one-byte disclosure.

7. Call-site confidence

Call-site confidence: high

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

Patch: Bluetooth: MGMT: Fix status of pending commands flushed on power off
Commit: 44ce36c5789ac84e65de1e98c32db9a5ac04ed47
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=44ce36c5789ac84e65de1e98c32db9a5ac04ed47

Commit description:

cmd_complete_rsp() receives a struct cmd_lookup and, for a pending
command that has no cmd_complete callback, falls through to
cmd_status_rsp(cmd, data). cmd_status_rsp() reads data as a u8 *, so
the status sent comes from the first byte of match->sk's
representation, not from match->mgmt_status.

commit f53e1c9 ("Bluetooth: MGMT: Fix possible crash on
mgmt_index_removed") changed the callers' data from &status to &match
and updated the cmd_complete branch to match->mgmt_status, but left
the fall-through passing data unchanged.

In mgmt_index_removed() match->sk is NULL, so every such command is
answered with status 0x00 (Success) instead of
MGMT_STATUS_INVALID_INDEX. In __mgmt_power_off() it is NULL too,
unless a Set Powered command was pending: then settings_rsp() has
stored that command's socket in match->sk, and the byte sent comes
from the socket pointer. Either way the status the caller set,
MGMT_STATUS_NOT_POWERED (or MGMT_STATUS_INVALID_INDEX when the device
is being unregistered), is lost.

Pass the status the callers set.

This was seen on a QCA9377 laptop: bluetoothd's Start Discovery,
pending when the adapter was powered off, was answered with Command
Status 0x00 and no parameters, and bluetoothd 5.72 crashed on the
zero-length success. BlueZ master has since added the length check
on that path ("adapter: Fix crash on short start discovery reply",
BlueZ a734b06059cb), but userspace should still be told Not Powered,
not Success.

Tested on Ubuntu 7.0.0-31 with a virtual controller (hci_vhci):
power off is held in HCI Write Scan Enable while a Start Discovery is
submitted, and the flush answers it with status 0x00 before this
change and 0x0f (Not Powered) after.

Fixes: f53e1c9 ("Bluetooth: MGMT: Fix possible crash on mgmt_index_removed")
Cc: stable@vger.kernel.org
Signed-off-by: Iaroslav Voitovych <yaroslav.voytovych@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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=44ce36c5789ac84e65de1e98c32db9a5ac04ed47

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

The original Linux kernel CVE announcement for CVE-2026-99091 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99091

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:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:L
  The Best / paranoid CVSS score: 3.6

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).