[CVE-2026-74532][MODERATE REGULAR] Bluetooth: btintel: Validate length before parsing diagnostics TLV [ Upstream

[CVE-2026-74532][MODERATE REGULAR] Bluetooth: btintel: Validate length before parsing diagnostics TLV [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74532
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: btintel: Validate length before parsing diagnostics TLV [ Upstream
Commit: c31be902ccbbb0b2c23159a1481dce80d1f9753d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c31be902ccbbb0b2c23159a1481dce80d1f9753d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74532
Analysis date: Sat, 15 Aug 2026 11:19:39 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
Bluetooth btintel diagnostics parsing can read beyond a short Intel diagnostics TLV before validating the frame length, creating a limited OOB read that may cause a warning or crash in controller-mediated conditions but does not show a write primitive or LPE path.

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

The original Linux kernel CVE announcement for CVE-2026-74532 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74532

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-74532	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H';CWE-125;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.9';DESCR 'btintel_diagnostics can read beyond the received HCI diagnostic frame because tlv val 0 is accessed before verifying that the Vendor Specific Event is long enough to contain the TLV value byte. This is an out-of-bounds read in the Bluetooth Intel diagnostics path and can plausibly cause a warning or kernel crash if a malformed short diagnostics frame is processed. For the CVSS the PR:N is used in the paranoid score because a nearby attacker or malicious Bluetooth endpoint may not need a local account if the malformed diagnostic event can be induced through the controller event path. The realistic base case is more restrictive and may require local privileged HCI control or a faulty or malicious controller. The issue is adjacent network reachable only under Bluetooth range and Intel diagnostics path assumptions. Impact is mainly denial of service, with at most limited confidentiality impact from an invalid read and no supported integrity impact.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 2)	YES	SIMPLEFIX SKB DEBUGFS  INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=3
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Limited read-only OOB / weak corruption: +0. The patch fixes an out-of-bounds read of `tlv->val[0]`, but there is no write, UAF, double-free, refcount abuse, type confusion, or attacker-controlled reclaim.
* Availability impact possible but not strong: +0. The commit says the bug may read beyond the received frame, but does not show a reliable panic, Oops, KASAN report, or host-wide crash.
* Rare AND difficult-to-reach subsystem/configuration: -1. This is Intel Bluetooth diagnostics VSE handling, not the common Bluetooth packet-processing path.
* Firmware/device-mediated path: +1. The malformed data reaches the kernel through HCI/controller diagnostic event handling.

Paranoid additional signals:

* Firmware-mediated external influence: +1. A malicious or compromised controller, or possibly a nearby Bluetooth actor able to induce malformed controller diagnostics, could influence the event path.
* Confidentiality impact plausible: +1. The primitive is an OOB read of one byte beyond the received frame, so limited unintended kernel/skb-adjacent data access is technically plausible, although no disclosure path is shown.
* Availability impact plausible: +1. A malformed short diagnostics frame may trigger a warning or crash on hardened/debug kernels or under unlucky skb layout conditions.

Not awarded:

* Remote reachable / network-triggerable +2 is not awarded. The affected input is a controller diagnostics VSE, not clearly a directly remote Bluetooth packet parser.
* Generic memory corruption +2 is not awarded. This is read-only OOB, not UAF/OOB write/type confusion.
* LPE plausibility is not awarded. No write primitive, stale callback, reclaim, refcount takeover, or object replacement is indicated.
* Integrity impact is not awarded.

## 3. Reachability analysis

The most direct trigger requires control over the Bluetooth HCI diagnostic event stream, which usually means a faulty, malicious, or compromised Intel Bluetooth controller, or privileged local HCI access. A normal unprivileged local user typically cannot directly inject arbitrary Intel diagnostic VSE frames. A nearby Bluetooth attacker might only be relevant if their traffic can cause the controller or firmware to emit a malformed diagnostics event, which is possible enough for paranoid triage but not demonstrated by the patch.

Namespaces and containers do not materially lower privileges unless the container is granted access to Bluetooth HCI management or raw HCI devices. The path is hardware and vendor specific, tied to Intel Bluetooth devcoredump diagnostics, so exposure is narrower than common Bluetooth L2CAP/SMP/RFCOMM receive paths.

Call-site confidence: medium. The changed function and immediate dereference are visible, but the full later use of `tlv->val[0]` and whether it can be disclosed or reliably crash is not included.

## 4. Severity interpretation

This behaves more like a low-to-borderline Moderate issue than an Important vulnerability. The theoretical concern is a limited out-of-bounds read in a wireless device path, but realistic exploitation evidence is weak because the patch does not show a user-visible leak, a reliable crash, memory corruption, or privilege escalation primitive. The paranoid score is raised to 3 to avoid auto-closing a vendor Bluetooth OOB read that may depend on firmware behavior and adjacent wireless influence.

## 5. One-sentence report phrase

Bluetooth btintel diagnostics parsing can read beyond a short Intel diagnostics TLV before validating the frame length, creating a limited OOB read that may cause a warning or crash in controller-mediated conditions but does not show a write primitive or LPE path.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is a vendor-specific Bluetooth OOB read with possible firmware-mediated or adjacent-wireless influence, but the demonstrated primitive is limited and does not justify Important-class handling without additional evidence.

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

Patch: Bluetooth: btintel: Validate length before parsing diagnostics TLV [ Upstream
Commit: c31be902ccbbb0b2c23159a1481dce80d1f9753d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c31be902ccbbb0b2c23159a1481dce80d1f9753d

Changed files:
  drivers/bluetooth/btintel.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=c31be902ccbbb0b2c23159a1481dce80d1f9753d

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

The original Linux kernel CVE announcement for CVE-2026-74532 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74532

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:L/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 5.9

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: 3

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).