[CVE-2026-46056][IMPORTANT] Bluetooth: hci_event: fix potential UAF in SSP passkey handlers

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

CVE: CVE-2026-46056
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: Bluetooth: hci_event: fix potential UAF in SSP passkey handlers
Commit: 204028af77a265e31ceb4ba7f643349a3cca72b2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=204028af77a265e31ceb4ba7f643349a3cca72b2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46056
Analysis date: Wed, 27 May 2026 10:57:02 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A Bluetooth-adjacent race in SSP passkey handlers can leave a stale `hci_conn` pointer in use after connection teardown, creating a kernel UAF with likely DoS impact and requiring review for broader memory-corruption risk.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-46056 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46056

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: IMPORTANT
Manual review required: YES

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-2026-46056	IMPORTANT	CHECK	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:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A use-after-free can occur in Bluetooth SSP passkey event handling because hci_conn lookup and later field access were not fully protected by hdev lock. A remote Bluetooth peer in adjacent radio range may influence passkey notification or keypress events while the connection is being torn down, leaving the handler with a stale hci_conn pointer. For the CVSS the PR:N is used because no local privileges are needed once the Bluetooth pairing path is reachable from an adjacent peer. AC:H is used because practical triggering requires a race between event processing and connection free. Impact is at least denial of service via kernel crash. Because this is a real UAF in Bluetooth event handling, worst-case confidentiality and integrity impact should be reviewed manually even though reliable exploitation is not demonstrated.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	REMOTE UAF NETWORK KPANIC 	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote-adjacent reachable: +2
  A Bluetooth peer in radio range can influence SSP passkey notification or keypress event flow during pairing or connection teardown.

* Generic memory corruption, strong corruption primitive: +2
  The commit explicitly identifies a potential UAF caused by accessing `hci_conn` after concurrent free.

* Real lifetime corruption: +1
  The issue is a lock coverage bug allowing connection lifetime to change while the handler still uses the object.

* Reliable kernel crash / strong DoS: +1
  A stale `hci_conn` pointer can cause kernel crash when fields are read or modified.

* Availability impact realistic: +1
  Successful triggering can disrupt the Bluetooth stack or crash the kernel.

Subtracting signals:

* Hard race / special timing required: -1
  Requires a race between SSP event handling and connection free.

* Adjacent/protocol-state constrained exposure: -1
  The attacker must be in Bluetooth range and reach the relevant pairing or passkey event state.

Paranoid additions:

* Privilege escalation plausible: +2
  UAF in a kernel network-adjacent protocol handler can sometimes be exploitable beyond crash if object reclaim and timing can be influenced, although no reliable primitive is shown.

## 3. Reachability analysis

A nearby Bluetooth device can potentially trigger relevant SSP passkey notification or keypress events while also causing connection teardown timing. No local account on the victim is needed, but the attacker must be within Bluetooth radio range and the affected pairing path must be reachable.

Namespaces and containers are not central. The bug is in kernel Bluetooth HCI event handling, which is commonly enabled on systems with Bluetooth hardware, but practical exposure depends on adapter presence, Bluetooth being enabled, pairing policy, and race timing.

## 4. Severity interpretation

This is at least Actionable Moderate and a Strong Important candidate under paranoid triage. It is not a simple NULL dereference or resource leak. The patch fixes a real UAF caused by insufficient lock coverage around `hci_conn` lookup and use.

Realistic exploitation evidence supports crash/DoS under a difficult race. Theoretical exploitation could be more serious because UAF is a strong memory-corruption class, but reliable privilege escalation is not demonstrated by the patch.

## 5. One-sentence report phrase

A Bluetooth-adjacent race in SSP passkey handlers can leave a stale `hci_conn` pointer in use after connection teardown, creating a kernel UAF with likely DoS impact and requiring review for broader memory-corruption risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a real UAF in a Bluetooth event path reachable from an adjacent peer under pairing/race conditions, so it should not be auto-closed despite the lack of a demonstrated exploit primitive.

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UPSTREAM PATCH SUMMARY
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Patch: Bluetooth: hci_event: fix potential UAF in SSP passkey handlers
Commit: 204028af77a265e31ceb4ba7f643349a3cca72b2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=204028af77a265e31ceb4ba7f643349a3cca72b2

Commit description:

hci_conn lookup and field access must be covered by hdev lock in
hci_user_passkey_notify_evt() and hci_keypress_notify_evt(), otherwise
the connection can be freed concurrently.

Extend the hci_dev_lock critical section to cover all conn usage in both
handlers.

Keep the existing keypress notification behavior unchanged by routing
the early exits through a common unlock path.

Fixes: 92a2525 ("Bluetooth: mgmt: Implement support for passkey notification")
Cc: stable@vger.kernel.org
Signed-off-by: Shuvam Pandey <shuvampandey1@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/hci_event.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=204028af77a265e31ceb4ba7f643349a3cca72b2

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

The original Linux kernel CVE announcement for CVE-2026-46056 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46056

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:N/I:N/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: 5
  Paranoid ActionableScore: 7

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).