[CVE-2026-98819][MODERATE REGULAR] Bluetooth: btintel: validate DDC record lengths [ Upstream

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

CVE: CVE-2026-98819
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: btintel: validate DDC record lengths [ Upstream
Commit: 069031f569f1681f17e863f48c221a6091b47850
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=069031f569f1681f17e863f48c221a6091b47850
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98819
Analysis date: Mon, 19 Oct 2026 02:42:45 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A malformed Intel Bluetooth DDC firmware record can wrap its parsed length to zero or make the kernel read beyond the firmware buffer, causing Bluetooth initialization failure and potentially transmitting adjacent kernel bytes to the controller, but reliable attacker-directed triggering requires control of the protected local firmware file.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-98819 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98819

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: 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-2026-98819	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98819 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF V39_AEGIS_ONE_STEP_UP=LOW->MODERATE TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:H';*CWE-20;CWE-125;CWE-190;*CWE-835;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.1';DESCR 'The btintel DDC parser stored a record length in u8 after adding one to a firmware supplied byte. A length byte of 0xFF could therefore wrap the computed length to zero and leave the parser without forward progress, while other malformed lengths could extend beyond the remaining firmware buffer. This creates a concrete out-of-bounds read that can pass adjacent kernel memory to the Bluetooth controller and can also cause Bluetooth initialization failure or a persistent parser loop. For the CVSS the PR:H reflects that reliable triggering normally requires control over a DDC firmware file loaded from a protected local firmware directory. The issue is not directly network reachable and the supplied code does not show that ordinary remote Bluetooth traffic can select the malformed record bytes. Impact is primarily local denial of service with possible limited confidentiality impact from the out-of-bounds read. There is no supported out-of-bounds write or UAF primitive in this change. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 5.1 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage LOW to MODERATE because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. 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. Exact triggered rule markers were KPANIC_UNSUPPORTED_REMOVED and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.2 and ActionableScore 0 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	SIMPLEFIX ERRORPATH SKB HARDWARE LINUS KPANIC_UNSUPPORTED_REMOVED V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=1
ActionableScoreLower=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap changed either score.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Conservative signals:

* +1 Firmware-mediated input influence. A malformed DDC firmware record directly controls the length parsed by `btintel_load_ddc_config()`.
* +1 Availability impact. A length byte of `0xFF` produces 256 before conversion to `u8`, resulting in zero and potentially preventing parser progress. Other rejected lengths can prevent Bluetooth initialization.
* -2 Host-admin-equivalent prerequisite. Reliable attacker-directed triggering requires installing or replacing the protected DDC firmware file. No less-privileged firmware injection path is supplied.
* Total: `1 + 1 - 2 = 0`.

Additional paranoid signal:

* +1 Confidentiality plausible. When the declared record length exceeds the remaining firmware bytes, `__hci_cmd_sync()` can copy bytes beyond the firmware buffer into an HCI command sent to the controller. This is a concrete device-visible OOB read, although attacker recovery of useful data is not established.
* Total: `1 + 1 + 1 - 2 = 1`.

Important non-awarded signals:

* No OOB write, UAF, double release, arbitrary write, controlled reclaim, or active structured-state corruption is established.
* No host-wide panic is demonstrated. The supported availability effect is primarily parser or Bluetooth-device initialization failure.
* No remote Bluetooth or network trigger is established because ordinary traffic does not supply the DDC file.
* NEW52 B5-R does not apply. There is no retry-accumulated heap OOB write or later consumption of corrupted structured state.
* NEW53 B3-PENDING does not apply. No shared-backing write exists.
* V33 and V32 do not apply. No attacker-controlled active networking metadata write exists.
* Authorization bypass and B4-PENDING do not apply.
* No integrity or privilege-escalation point is awarded.

3. Reachability analysis

The parser consumes a DDC blob obtained through the kernel firmware-loading path during Intel Bluetooth initialization. The supplied evidence does not show that a remote Bluetooth peer, ordinary local user, network namespace, or delegated interface can provide these bytes.

Reliable malicious triggering therefore requires control of the local DDC firmware file or its trusted distribution path. That normally requires host-administrator-equivalent authority. Numeric host UID 0 specifically is not proven because equivalent capabilities or another privileged firmware-management mechanism could modify the file.

No namespace-scoped operation, race, retry sequence, special boot option, or rare physical attack is required. Intel Bluetooth hardware and a malformed DDC blob are prerequisites. The `0xFF` wrap condition is deterministic once such a blob is loaded.

4. Primitive and severity interpretation

The exact primitive is a malformed-length parser defect with two consequences:

1. `fw_ptr[0] + 1` can equal 256 and truncate to zero when stored in `u8`, potentially preventing forward progress.
2. A nonzero length greater than the remaining firmware data can make `__hci_cmd_sync()` read beyond the firmware buffer and transmit those bytes to the controller.

This is a read-only OOB condition and invalid parser state, not kernel-memory modification. It is therefore `CLASS_C`, not Class A or Class B. The demonstrated practical consequence is Bluetooth initialization failure or parser stalling. A limited disclosure to the controller is technically plausible, but useful attacker observation and a protected-data consequence remain unproven.

`ImportantCandidate=NO` because there is no write primitive, lifetime violation, authorization bypass, shared-backing corruption, or credible below-host-admin boundary crossing. `AutoDowngradeAllowed=YES` because the remaining primitive is constrained and the complete malicious trigger requires control of protected firmware input.

5. One-sentence report phrase

A malformed Intel Bluetooth DDC firmware record can wrap its parsed length to zero or make the kernel read beyond the firmware buffer, causing Bluetooth initialization failure and potentially transmitting adjacent kernel bytes to the controller, but reliable attacker-directed triggering requires control of the protected local firmware file.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm whether any product-specific firmware helper or update service permits a below-host-admin actor to supply DDC files and whether controller-visible OOB bytes can be recovered by an attacker. Without such a path, the issue is suitable for low-priority handling.

7. Call-site confidence

Call-site confidence: medium

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

Patch: Bluetooth: btintel: validate DDC record lengths [ Upstream
Commit: 069031f569f1681f17e863f48c221a6091b47850
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=069031f569f1681f17e863f48c221a6091b47850

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=069031f569f1681f17e863f48c221a6091b47850

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

The original Linux kernel CVE announcement for CVE-2026-98819 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98819

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:L/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 5.1

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: 0
  Paranoid ActionableScore: 1

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).