[CVE-2026-74507][MODERATE REGULAR] Bluetooth: HIDP: validate numbered report payloads

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

CVE: CVE-2026-74507
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Bluetooth: HIDP: validate numbered report payloads
Commit: b7ad105d46acd828e424454815e4cd31069e047a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b7ad105d46acd828e424454815e4cd31069e047a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74507
Analysis date: Sat, 15 Aug 2026 16:47:23 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline manual review recommended / Ordinary Moderate with adjacent-network invalid-read concern
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-74507 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74507

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-2026-74507	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N';CWE-125;CWE-908;*CWE-20;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N';BEST CVSS score: '5.4';DESCR 'A malformed Bluetooth HIDP numbered report can be processed without verifying that a payload byte is present after the DATA transaction header is removed. A connected HIDP peer can send an empty or truncated DATA response and cause hidp_process_data to compare the expected report ID against skb data 0 even when the skb payload is empty. For the CVSS the PR:N is used because a malicious connected HIDP peer does not need a local account on the target once the Bluetooth HIDP session exists. The issue is adjacent network reachable over Bluetooth rather than Internet reachable. Impact is mainly low integrity because a malformed FEATURE response may be accepted and complete HIDIOCGFEATURE with an invalid zero byte result. Paranoid impact also includes low confidentiality because an uninitialized or out of bounds byte can influence kernel control flow, but no reliable kernel crash or privilege escalation primitive is evident from the patch.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Ordinary Moderate with adjacent-network invalid-read concern (with actual score 4)	YES	REMOTE WRITE KASAN OOB USB NETWORK SKB  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline manual review recommended / Ordinary Moderate with adjacent-network invalid-read concern**

2. Signal breakdown
* Remote reachable / network-triggerable: +2. The trigger is a connected Bluetooth HIDP peer sending malformed DATA / FEATURE responses. This is adjacent-network Bluetooth reachability, not Internet AV:N.
* Integrity impact plausible: +1. The malformed response can be accepted as a numbered report and complete HIDIOCGFEATURE with an invalid zero-byte result.
* Confidentiality impact plausible: +1 in paranoid score only. KMSAN reports uninitialized-value use and the comparison may consume a byte beyond the declared L2CAP PDU, but there is no clear user-visible disclosure primitive.
* Weak corruption / invalid read: +0. This is an uninitialized or out-of-bounds read used in a comparison, not UAF, OOB write, double-free, type confusion, or arbitrary write.
* Reliable kernel crash / strong DoS: +0. The patch does not show a reliable panic or host-wide crash.
* Privilege escalation plausible: +0. No reclaim, overwrite, stale callback, refcount takeover, or controlled memory corruption primitive is shown.

3. Reachability analysis
A malicious connected Bluetooth HIDP peer can trigger the bug by replying with an empty or malformed numbered report payload after the transaction header is removed. No local account on the victim is required once the HIDP session exists, but the attacker needs Bluetooth adjacency and a paired or otherwise connected HIDP path. Namespaces and containers do not materially lower or raise the trigger requirement because the input comes from the Bluetooth peer side. The path is not a broad Internet-facing network path, but Bluetooth HID support is common on systems using Bluetooth input devices.

4. Severity interpretation
This behaves like an ordinary Moderate issue with manual-review value, not an Important-class kernel vulnerability based on the supplied patch. The theoretical concern is an invalid or uninitialized kernel read influencing control flow and accepting malformed report state. Realistic exploitation evidence supports low integrity impact and possibly low confidentiality concern, but not memory corruption, kernel code execution, or local privilege escalation.

5. One-sentence report phrase
A connected Bluetooth HIDP peer can send an empty or malformed numbered DATA report so hidp_process_data reads skb data 0 without a payload byte, causing uninitialized or out-of-bounds byte use and possible malformed HIDIOCGFEATURE completion.

6. Manual review recommendation
MANUAL CHECK REQUIRED.
Reason: the issue is adjacent-network reachable over Bluetooth and involves an uninitialized or out-of-bounds kernel read, even though the demonstrated impact appears limited and no strong LPE or crash primitive is shown.

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

Patch: Bluetooth: HIDP: validate numbered report payloads
Commit: b7ad105d46acd828e424454815e4cd31069e047a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b7ad105d46acd828e424454815e4cd31069e047a

Commit description:

When hidp_get_raw_report() waits for a numbered report,
hidp_process_data() compares the expected report number with skb->data[0].
A connected HIDP peer can reply with only a DATA transaction header,
leaving the skb empty after the header is removed.

KMSAN reports an uninitialized-value use in hidp_session_run(), with the
value originating in __alloc_skb() through vhci_write(). The transaction
header checks remove the empty-frame reports, but this report remains until
the payload check is added.

The comparison can also consume a peer-controlled byte beyond the declared
L2CAP PDU. A DATA | FEATURE response followed by an extra 0x01 byte made
the current code accept that byte as report ID 1 and complete
HIDIOCGFEATURE with a zero-byte result. With this change the malformed
response is rejected with -EIO, while a subsequent valid response still
succeeds.

Require a payload byte before comparing a numbered report ID. Unnumbered
reports continue to accept an empty payload.

Fixes: 0ff1731 ("HID: bt: Add support for hidraw HIDIOCGFEATURE and HIDIOCSFEATURE")
Cc: stable@vger.kernel.org
Signed-off-by: Sangho Lee <kudo3228@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:
  net/bluetooth/hidp/core.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=b7ad105d46acd828e424454815e4cd31069e047a

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

The original Linux kernel CVE announcement for CVE-2026-74507 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74507

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:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
  The Best / paranoid CVSS score: 5.4

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).