[CVE-2026-64407][MODERATE REGULAR] Bluetooth: btnxpuart: Fix out-of-bounds firmware read in nxp_recv_fw_req_v3()

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

CVE: CVE-2026-64407
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: btnxpuart: Fix out-of-bounds firmware read in nxp_recv_fw_req_v3()
Commit: 21e60eb4d95854196e7c0e77383f35e7ac95df61
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21e60eb4d95854196e7c0e77383f35e7ac95df61
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64407
Analysis date: Sat, 25 Jul 2026 08:53:24 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline manual review / Actionable Moderate candidate
Manual review required: YES

Summary:
A malicious or compromised NXP Bluetooth controller can request firmware data outside the firmware image during v3 download, causing the host kernel driver to read adjacent kernel memory and send it back over UART.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64407 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64407

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 REGULAR
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-2026-64407	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H';CWE-125;*CWE-200;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:L';BEST CVSS score: '6.1';DESCR 'An out of bounds read in the Bluetooth btnxpuart firmware download path occurs because nxp_recv_fw_req_v3 accepts a controller supplied 32 bit offset and 16 bit length but did not verify that offset plus length stays within the firmware image. A malicious or compromised NXP Bluetooth controller can request data past nxpdev fw data and the host driver will send bytes from adjacent kernel memory back over UART. For the CVSS the PR:N is used because the attacker does not need host user privileges if the hostile controller is already attached or compromised. The issue is not directly reachable from the IP network and is not a normal remote Bluetooth peer attack because the vulnerable path runs during controller firmware download. Impact is primarily confidentiality loss from kernel memory disclosure and may also cause denial of service if the out of bounds read faults.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review / Actionable Moderate candidate (with actual score 4)  SKIP CVE-2026-64407 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WRITE OOB SIMPLEFIX ERRORPATH SKB IMPROVEONLY  INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline manual review / Actionable Moderate candidate**::

## 2. Signal breakdown

* Firmware-mediated external influence: +1. The hostile input comes from the Bluetooth controller during firmware download, not from a normal local syscall or IP network peer.
* Confidentiality impact plausible: +1. The driver can read past `nxpdev->fw->data` and send adjacent kernel memory back over UART.
* Practical exploit chain strongly implied: +1. The commit directly describes controller-chosen `offset` and `len` causing out-of-bounds host memory disclosure.
* Availability impact realistic, paranoid only: +1. If the out-of-bounds read crosses into unmapped or faulting memory, a kernel crash is possible.
* Limited read-only OOB: +0. This is an OOB read and disclosure primitive, not an OOB write, UAF, double free, or type confusion.
* No LPE signal: +0. The patch does not show attacker-controlled overwrite, reclaim, callback control, or object confusion.
* No remote-network signal: +0. This is not realistically reachable from an IP network or ordinary Bluetooth peer traffic.

## 3. Reachability analysis

The realistic trigger is a malicious, compromised, or emulated NXP Bluetooth controller that can send crafted v3 firmware download requests. A normal remote Bluetooth peer should not be able to reach this firmware-download path directly. No host user privileges are needed if the attacker controls the controller side, but practical exploitation depends on firmware compromise, malicious hardware, supply-chain attack, physical replacement, or a test/emulation setup. Namespaces and containers do not materially change reachability because the vulnerable input is device-controller mediated rather than a container-visible local API.

## 4. Severity interpretation

This behaves like an actionable information disclosure issue rather than a generic DoS-only bug. The primitive is a bounded-by-controller out-of-bounds read from kernel memory adjacent to the firmware buffer, with direct transmission back over UART. It does not currently justify Important-class LPE treatment because there is no write primitive or lifetime corruption, but it should not be auto-closed as ordinary Low because the confidentiality path is concrete.

## 5. One-sentence report phrase

A malicious or compromised NXP Bluetooth controller can request firmware data outside the firmware image during v3 download, causing the host kernel driver to read adjacent kernel memory and send it back over UART.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. The issue has a concrete kernel OOB read and disclosure path, even though exploitation requires controller-side influence rather than ordinary remote network access.

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UPSTREAM PATCH SUMMARY
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Patch: Bluetooth: btnxpuart: Fix out-of-bounds firmware read in nxp_recv_fw_req_v3()
Commit: 21e60eb4d95854196e7c0e77383f35e7ac95df61
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21e60eb4d95854196e7c0e77383f35e7ac95df61

Commit description:

During the v3 firmware download the controller sends a v3_data_req with a
32 bit offset and a 16 bit len. nxp_recv_fw_req_v3() checks only the lower
bound of the offset and then sends firmware from that offset.

  nxpdev->fw_dnld_v3_offset = offset - nxpdev->fw_v3_offset_correction;
  serdev_device_write_buf(nxpdev->serdev, nxpdev->fw->data +
                          nxpdev->fw_dnld_v3_offset, len);

Nothing checks that fw_dnld_v3_offset + len stays within nxpdev->fw->size,
so a controller that asks for an offset or length past the firmware image
makes the driver read past the end of nxpdev->fw->data and send that
memory back over UART.

nxp_recv_fw_req_v1() already bounds the same write. Add the equivalent
check to the v3 path, reject the request when it falls outside the firmware
image, and zero len on the error path so the fw_v3_prev_sent bookkeeping at
free_skb stays consistent.

Fixes: 689ca16 ("Bluetooth: NXP: Add protocol support for NXP Bluetooth chipsets")
Suggested-by: Neeraj Sanjay Kale <neeraj.sanjaykale@nxp.com>
Reviewed-by: Neeraj Sanjay Kale <neeraj.sanjaykale@nxp.com>
Cc: stable@vger.kernel.org
Signed-off-by: Maoyi Xie <maoyixie.tju@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:
  drivers/bluetooth/btnxpuart.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=21e60eb4d95854196e7c0e77383f35e7ac95df61

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

The original Linux kernel CVE announcement for CVE-2026-64407 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64407

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:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:L
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
  The Best / paranoid CVSS score: 6.1

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: 4

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 REGULAR

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).