[CVE-2026-97907][LOW] Bluetooth: btrtl: Don't leak return code when parsing firmware format v2

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

CVE: CVE-2026-97907
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: Bluetooth: btrtl: Don't leak return code when parsing firmware format v2
Commit: 90f3a142b5f8596a565b8e080d18a8050be6edef
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=90f3a142b5f8596a565b8e080d18a8050be6edef
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97907
Analysis date: Sat, 26 Sep 2026 14:35:13 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A Realtek Bluetooth firmware v2 parser control-flow error can use an uninitialized or stale return code when ignored security headers are processed, potentially causing local Bluetooth adapter initialization failure without establishing kernel memory corruption or privilege escalation.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-97907 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97907

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-2026-97907	LOW	https://www.kernelcve.org/list/?q=CVE-2026-97907 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';*CWE-457;CWE-670;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '2.3';DESCR 'A logic error in the Realtek Bluetooth firmware v2 parser can use an uninitialized return code or a return code left from a previous firmware section when security headers are ignored for a chip with key_id equal to zero. This can incorrectly abort firmware parsing and prevent Bluetooth device initialization, resulting in a local availability issue for the affected Bluetooth adapter. For the CVSS the PR:H reflects that reliable triggering normally requires control of the firmware input, Bluetooth device administration, or driver load conditions. The issue is not network reachable through Bluetooth traffic and no memory corruption, information disclosure, integrity impact, or privilege escalation primitive is indicated by the code path. The impact is limited to Bluetooth functionality denial of service.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	YES	SIMPLEFIX LEAK 	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

## 1. ActionableScore

* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate**::

The patch establishes a parser control-flow defect and a possible device-local Bluetooth initialization failure. It does not establish a kernel corruption, lifetime, authorization, disclosure, or security-boundary primitive.

## 2. Signal breakdown

* +0 Uninitialized scalar return code use: `rc` may be uninitialized when the first ignored security section is processed, or may retain a result from an earlier section. This is a concrete logic defect, but it is not a pointer dereference, memory write, lifetime mutation, or active-object corruption primitive.
* +0 Device-local functional impact: an erroneous negative `rc` can abort Realtek Bluetooth firmware parsing and prevent initialization of the affected Bluetooth adapter. The supplied patch does not establish a host crash, panic, system-wide denial of service, persistent resource exhaustion, or filesystem shutdown.
* +0 Remote reachability not established: Bluetooth traffic is not shown to reach `rtlbt_parse_firmware_v2`. The parser operates on firmware loaded for the local Bluetooth device.
* +0 Controlled firmware input not established: the supplied patch does not establish that an ordinary user, a nearby Bluetooth peer, or another remote actor can replace the firmware file or alter the chip `key_id`.
* +0 Confidentiality not awarded: although an uninitialized scalar can theoretically carry prior stack/register contents, the visible path only compares `rc < 0` and may log or return an error. No user-visible disclosure path is established.
* +0 Integrity not awarded: no write, object replacement, refcount mutation, ownership violation, or authorization bypass is present.
* +0 Availability crash bonus not awarded: the demonstrated consequence is firmware parse failure and Bluetooth adapter initialization failure, not a kernel crash.
* +0 UAF/lifetime signals not awarded: there is no free, put, release, stale object access, second lifetime mutation, RCU issue, or refcount operation.
* +0 No paranoid escalation: lowering attack complexity would not create a stronger primitive. The defect remains an incorrect parser return-value/control-flow condition.

## 3. Reachability analysis

The affected function parses Realtek Bluetooth firmware v2 during local device initialization. The relevant conditions are a chip with `key_id` equal to zero and firmware containing ignored security-header sections, especially when such a section appears before a section that initializes `rc`.

The supplied evidence does not establish the complete privilege boundary for controlling the firmware file, loading/reloading the driver, or exposing a matching Bluetooth device. Therefore, `HostAdminRequired=UNKNOWN` is appropriate rather than assuming either host-admin access or ordinary-user reachability.

No namespace-scoped capability path is shown. Network namespaces, Bluetooth namespaces, containers, nearby Bluetooth devices, and ordinary Bluetooth packet traffic are not shown to provide control over this firmware parser path. Therefore, `NamespaceScopedPrivilege=UNKNOWN`.

No race, special timing condition, DMA interaction, or attacker-controlled hardware payload is established.

## 4. Primitive and severity interpretation

The exact primitive is an uninitialized or stale scalar error-code value used after a `switch` branch intended to ignore firmware sections. `break` exits the `switch` but reaches the subsequent `if (rc < 0)` check. Replacing it with `continue` skips the loop iteration as intended.

This is neither active structured-object corruption nor fixed stale storage. It is a parser logic bug involving scalar control state.

There is no concrete repeated release/refcount operation. No first lifetime operation may free an object, no dangling reference survives, and no second lifetime/refcount mutation occurs.

The demonstrated consequence is an erroneous firmware parsing failure, potentially leaving the affected Bluetooth adapter unavailable until a corrected driver/firmware initialization path is used. A privilege escalation, kernel crash, information disclosure, arbitrary write, or security-boundary bypass is speculative and unsupported.

`PrimitiveClass=NONE` because no meaningful corruption, ownership, lifetime, authorization, or similar security primitive is established. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` because the patch does not leave an unresolved kernel-corruption or boundary-bypass mechanism requiring Important-versus-Moderate review.

## 5. One-sentence report phrase

A Realtek Bluetooth firmware v2 parser control-flow error can use an uninitialized or stale return code when ignored security headers are processed, potentially causing local Bluetooth adapter initialization failure without establishing kernel memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch is a localized scalar return-code/control-flow correction with device-local availability impact only. No concrete memory corruption, UAF, authorization bypass, remote trigger, or persistent resource-exhaustion mechanism is shown.

## 7. Call-site confidence

Call-site confidence: medium

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

Patch: Bluetooth: btrtl: Don't leak return code when parsing firmware format v2
Commit: 90f3a142b5f8596a565b8e080d18a8050be6edef
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=90f3a142b5f8596a565b8e080d18a8050be6edef

Commit description:

When key_id from chip is zero, rtlbt_parse_firmware_v2() intentionally
ignores all security headers. However, the implementation simply breaks
from a switch statement and leaks uninitialized return code `rc' (if the
first section is a security one) or the previous section's `rc'.

Fix it by really skipping a loop with `continue'. For consistency and
readability, also do the same for the default case.

Fixes: 9a24ce5 ("Bluetooth: btrtl: Firmware format v2 support")
Cc: stable@vger.kernel.org
Signed-off-by: Rong Zhang <i@rong.moe>
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/btrtl.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=90f3a142b5f8596a565b8e080d18a8050be6edef

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

The original Linux kernel CVE announcement for CVE-2026-97907 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97907

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:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS score: 2.3

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: unknown
  Paranoid ActionableScore: 0

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).