[CVE-2026-80765][MODERATE 7.0] HID: hyperv: validate initial device info bounds

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

CVE: CVE-2026-80765
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: HID: hyperv: validate initial device info bounds
Commit: e0d5d3e45e142b7ef7525654aaa54d3e986002a6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0d5d3e45e142b7ef7525654aaa54d3e986002a6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80765
Analysis date: Fri, 04 Sep 2026 16:24:17 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline manual review recommended. Actionable Moderate at minimum
Manual review required: YES

Summary:
A malformed Hyper-V synthetic HID initial device info message can make the Linux guest read past the received VMBus packet while copying the HID report descriptor, causing a guest kernel crash and possible limited confidentiality concern from an OOB read.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-80765 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80765

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 7.0
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-2026-80765	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80765 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:L/I:N/A:H';CWE-125;*CWE-20;CWE-130;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.1';DESCR 'A bounds validation bug in the Hyper-V HID guest driver allows a malformed SYNTH_HID_INITIAL_DEVICE_INFO message to make the guest read past the received VMBus packet while copying the HID report descriptor. A malicious Hyper-V host or backend can trigger this by sending a short initial device info message with oversized HID descriptor or report descriptor length fields, causing a guest kernel crash. For the CVSS the PR:H is used because reliable triggering normally requires control over the Hyper-V host side or backend that supplies synthetic HID messages to the guest. The issue is not network reachable and is a host to guest virtualization path rather than packet traffic. Impact is primarily denial of service of the guest. The paranoid score keeps limited confidentiality impact because the primitive is an out-of-bounds read in guest kernel context, but there is no clear write primitive or privilege escalation path supported by the patch.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended. Actionable Moderate at minimum (with actual score 4)	YES	USB WARNONLY HARDWARE LINUS PACKET  KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline manual review recommended. Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Firmware-mediated external influence: +1
  The malformed input comes from the Hyper-V host side or backend over VMBus, not from ordinary guest-local users or Internet networking.

* Reliable kernel crash / strong DoS: +1
  The commit explicitly states that a short initial device-info message with oversized descriptor lengths can crash the guest.

* Broad/default/common subsystem in affected environment: +1
  The Hyper-V HID guest driver is a normal synthetic device path for Linux guests running under Hyper-V, although it is not a universal bare-metal kernel exposure.

Paranoid additional signal:

* Confidentiality impact plausible: +1
  The primitive is an out-of-bounds read in guest kernel context while copying descriptor data. No concrete disclosure path is shown, but limited C impact is defensible for manual triage.

Signals not awarded:

* No remote/network-triggerable +2
  This is not reachable through normal network packets.

* No strong memory corruption +2
  The patch shows OOB read and guest crash, not OOB write, UAF, double free, type confusion, or arbitrary write.

* No privilege escalation plausible +2
  There is no supported local guest-to-root or guest-to-host escalation primitive.

* No integrity impact +1
  The patch does not show attacker-controlled writes or corruption of guest kernel objects.

## 3. Reachability analysis

The bug is triggered by a malformed `SYNTH_HID_INITIAL_DEVICE_INFO` message delivered by the Hyper-V synthetic HID host/backend to the Linux guest. A normal unprivileged process inside the guest is not expected to control this message path directly. Realistic triggering requires a malicious or compromised Hyper-V host side, backend implementation, or equivalent control over the synthetic device channel.

Namespaces and containers inside the guest do not materially lower the privilege requirement because the vulnerable input is supplied by the virtualization host/device side, not by an in-guest namespace interface. The path is relevant mainly for Linux systems running as Hyper-V guests with the hid-hyperv driver active.

## 4. Severity interpretation

This behaves more like an actionable Moderate virtualization-boundary DoS than an Important-class kernel vulnerability. The demonstrated impact is guest kernel crash from an OOB read while copying HID report descriptor data. The theoretical memory-safety concern is real enough for manual review, but the evidence does not support strong memory corruption, privilege escalation, arbitrary code execution, or guest-to-host impact.

## 5. One-sentence report phrase

A malformed Hyper-V synthetic HID initial device info message can make the Linux guest read past the received VMBus packet while copying the HID report descriptor, causing a guest kernel crash and possible limited confidentiality concern from an OOB read.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is a virtualization-boundary OOB read with reliable guest DoS and possible limited confidentiality concern, but no demonstrated write primitive or privilege escalation path.

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

Patch: HID: hyperv: validate initial device info bounds
Commit: e0d5d3e45e142b7ef7525654aaa54d3e986002a6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0d5d3e45e142b7ef7525654aaa54d3e986002a6

Commit description:

The Hyper-V synthetic HID host supplies SYNTH_HID_INITIAL_DEVICE_INFO
messages that contain a HID descriptor followed by the report descriptor
bytes. mousevsc_on_receive_device_info() trusts bLength and
wDescriptorLength without checking that the received packet contains both
byte ranges.

A malformed host or backend message can therefore make the guest read
past the received VMBus packet while copying the report descriptor. Pass
the received initial-device-info size into the parser and reject
descriptor lengths that exceed the packet.

Impact: A malicious Hyper-V host or backend can crash a guest by sending
a short initial device-info message with an oversized HID report
descriptor length.

Fixes: b95f5bc ("HID: Move the hid-hyperv driver out of staging")
Cc: stable@vger.kernel.org
Assisted-by: Codex:gpt-5-5-xhigh
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/hid/hid-hyperv.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=e0d5d3e45e142b7ef7525654aaa54d3e986002a6

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

The original Linux kernel CVE announcement for CVE-2026-80765 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80765

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:H
  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: 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: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).