[CVE-2026-98731][LOW] Bluetooth: btintel_pcie: fix plen overflow in btintel_pcie_recv_frame()

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

CVE: CVE-2026-98731
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: Bluetooth: btintel_pcie: fix plen overflow in btintel_pcie_recv_frame()
Commit: c3a3842c109ac130c6db3aa0014cc8cd344928ad
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c3a3842c109ac130c6db3aa0014cc8cd344928ad
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98731
Analysis date: Sat, 24 Oct 2026 05:16:33 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A 16-bit packet-length wrap can incorrectly truncate a Bluetooth PCIe receive skb, with no demonstrated memory corruption or security-boundary impact.

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

The original Linux kernel CVE announcement for CVE-2026-98731 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98731

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
======================================================================

CVE-2026-98731	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98731 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both 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:N/I:N/A:L';CWE-190;*CWE-20;CWE-681;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.1';DESCR 'An unsigned 16 bit overflow in btintel_pcie_recv_frame can make HDR_SIZE plus dlen wrap when an ACL or ISO frame reports a length of at least 0xFFFC. The wrapped plen can bypass the skb length check and cause skb_trim to truncate the frame to an incorrect small size. The demonstrated primitive is malformed packet truncation rather than an OOB access, UAF, information leak, or arbitrary write. For the CVSS the PR:N in the paranoid vector reflects that an adjacent Bluetooth peer would need no local account if radio traffic can make the controller emit the anomalous HCI length. That reachability is not established because the controller or its firmware normally creates the PCIe HCI length and ordinary Bluetooth traffic is subject to much smaller protocol limits. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 3.1 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. 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. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	MAYBE	SIMPLEFIX IMPROVEONLY LINUS 	-	-	checked

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

ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 0.
* Conservative score: 0; no floor or cap applied.
* Raw paranoid score: 0.
* Paranoid score: 0; speculative Bluetooth-peer influence is not scored.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +0 — The confirmed `u16` arithmetic wrap lets a large ACL/ISO `dlen` bypass the length check and makes `skb_trim()` truncate the skb to an incorrect small length.
* No corruption bonus: `skb_trim()` shortens an existing skb; the evidence does not show an OOB read/write, UAF, stale pointer, or overwrite.
* No DoS point: malformed truncation is shown, but no kernel crash, persistent device failure, or host-wide availability effect is established.
* No remote/firmware-mediated point: an adjacent peer’s ability to make the controller emit the anomalous 16-bit HCI length is not established.
* No authorization signal: there is no DENY-to-ALLOW security decision or protected-resource access.
* NEW52/B5-R does not apply: there is no retry-accumulated index and no heap OOB write.
* NEW53/B3-PENDING does not apply: no shared/file-backed write is shown.

3. Reachability analysis

The malformed length comes from the PCIe Bluetooth receive path, apparently through controller/firmware-produced HCI framing. The supplied evidence does not establish whether ordinary radio traffic, a malicious peer, compromised firmware, physical device manipulation, or host administration can produce `dlen >= 0xFFFC`. Consequently, complete trigger privilege and hardware/firmware prerequisites remain unknown; namespace-scoped capability access is not implicated.

4. Primitive and severity reading

The exact defect is integer truncation causing an incorrect in-buffer skb length reduction. It is neither active structured-state corruption nor a lifetime violation. Later unsafe consumption is not shown; the visible result is only a malformed shortened frame. Stronger crash, disclosure, integrity, or code-execution effects are speculative. Therefore the classification is `NONE`, with no Important-preserving primitive and auto-downgrade permitted.

5. One-sentence report phrase

A 16-bit packet-length wrap can incorrectly truncate a Bluetooth PCIe receive skb, with no demonstrated memory corruption or security-boundary impact.

6. Manual review advice

NO MANUAL CHECK NEEDED

The patch-supported effect is limited to malformed skb truncation, while attacker reachability and any material downstream consequence are unproven.

7. Call-site confidence

Call-site confidence: medium

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

Patch: Bluetooth: btintel_pcie: fix plen overflow in btintel_pcie_recv_frame()
Commit: c3a3842c109ac130c6db3aa0014cc8cd344928ad
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c3a3842c109ac130c6db3aa0014cc8cd344928ad

Commit description:

plen is u16 and computed as HDR_SIZE + dlen. For ACL/ISO frames dlen
is a 16-bit field, so a value >= 0xFFFC wraps the sum, bypassing the
"skb->len < plen" check and letting skb_trim() truncate the packet.

Widen plen to u32 so the addition cannot wrap.

Fixes: c2b636b ("Bluetooth: btintel_pcie: Add support for PCIe transport")
Cc: stable@vger.kernel.org
Signed-off-by: Chandrashekar Devegowda <chandrashekar.devegowda@intel.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/btintel_pcie.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=c3a3842c109ac130c6db3aa0014cc8cd344928ad

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

The original Linux kernel CVE announcement for CVE-2026-98731 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98731

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:H/PR:N/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:N/I:N/A:L
  The Best / paranoid CVSS score: 3.1

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: 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).