* [CVE-2026-90197][MODERATE REGULAR] HID: haptic: don't write an uninitialized value to unhandled usages [ Upstream
@ 2026-09-18 1:25 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-18 1:25 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-90197
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: HID: haptic: don't write an uninitialized value to unhandled usages [ Upstream
Commit: 324cc98b71f0d3dee7367ef3c669fd80747e71b6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=324cc98b71f0d3dee7367ef3c669fd80747e71b6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90197
Analysis date: Thu, 17 Sep 2026 21:25:03 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90197 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90197
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-2026-90197 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90197 CHECK WITH IMPACT FROM ORIG NN MODERATE 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:N/A:N';*CWE-457;*CWE-200;CWE-201;Other CVSS 'AV:P/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N';BEST CVSS score: '4.3';DESCR 'An uninitialized value in HID haptic fill_effect_buf() can be copied into a field for an unhandled usage and later serialized by hid_output_report() into a report sent to the connected device. A malicious HID device may therefore receive a small amount of stale kernel stack data when a haptic effect is generated. For the CVSS the PR:N value is used because an attacker controlling a connected or paired HID peripheral does not require an account or privileges in the victim operating system. The base score uses physical access and user interaction for the normal USB device scenario. The paranoid score uses adjacent access for a previously paired Bluetooth HID device and assumes that normal software generates the affected haptic report without additional user action. Impact is limited to potential confidentiality loss. There is no supported host memory corruption, integrity impact, privilege escalation, or denial of service primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) SKIP CVE-2026-90197 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE READ USB SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 3
* Paranoid score: 3
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
Positive signals:
* +1 Confidentiality plausible. An uninitialized scalar is copied into the HID field and serialized into a device-visible output report.
* +1 Practical disclosure chain. The commit directly establishes the sequence from an unhandled usage through `field->value[j]` to `hid_output_report()`.
* +1 Firmware-mediated external influence. Exploitation requires a connected HID peripheral with relevant usage descriptors and the device receives the resulting report.
Total: 3.
Non-awarded signals:
* No UAF, OOB write, arbitrary write, controlled reclaim, callback influence, or kernel control-flow corruption is established.
* No integrity or availability point is awarded. The incorrect value affects the peripheral report and no host corruption or crash is shown.
* Direct remote reachability is not established. A Bluetooth device may provide adjacent exposure, but this remains device-mediated.
* Strong disclosure is not awarded because the visible primitive appears limited to one scalar value per affected usage.
* Important-grade leverage is not awarded because repeated extraction of sensitive data, stable stack-content control, or a mitigation-bypass chain is not demonstrated.
* No physical-only penalty is applied because the supplied context also presents a potentially paired Bluetooth HID scenario. Physical access is therefore not established as the exclusive path.
3. Reachability analysis
The direct attacker model is a malicious connected HID haptic device that supplies a descriptor containing an unhandled usage and receives output reports. The normal USB scenario requires physical device attachment and generation of a haptic effect by host software. A previously paired malicious Bluetooth HID device may provide adjacent reachability, but the supplied patch does not establish pairing bypass or direct remote triggering.
The peripheral attacker does not need a host account or host-administrator privilege after the device is connected and exercised, so `HostAdminRequired=NO`. No user-namespace or namespace-scoped capability participates in the path, so `NamespaceScopedPrivilege=NO`.
No special race is involved. Trigger reliability depends on reaching `fill_effect_buf()` with an unhandled usage and causing the host to emit the corresponding effect report. The precise number of exposed bytes and whether repeated reports disclose useful changing stack contents remain unresolved.
4. Primitive and severity interpretation
The exact primitive is a limited uninitialized kernel-stack value disclosure to a connected HID peripheral. The value is written into a report field and then serialized, so this is more than an internal uninitialized read.
This is not stale storage, a lifetime violation, or a repeated release operation. `RealUAF=NO`. It is classified as constrained `CLASS_B` because a concrete device-visible disclosure primitive exists, but it is not substantial enough for `CLASS_A`.
The demonstrated consequence is limited confidentiality exposure. Potential repetition or disclosure of security-sensitive stack contents is plausible but not established. Host memory modification, privilege escalation, and denial of service are unsupported.
`ImportantCandidate=NO` because there is no strong corruption, substantial disclosure, or boundary-bypass primitive. `AutoDowngradeAllowed=YES` because the established primitive is narrow and no unresolved Important-grade leverage is visible. Operationally, this is a Low-like to borderline Moderate information-disclosure issue.
5. One-sentence report phrase
An unhandled HID haptic usage can cause an uninitialized kernel stack value to be serialized into an output report visible to a malicious connected peripheral, resulting in a limited information disclosure.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Confirm the scalar width, report repetition behavior, stack-value stability, affected HID transports, and whether Bluetooth permits a practical adjacent attacker to collect enough output for a useful disclosure.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: HID: haptic: don't write an uninitialized value to unhandled usages [ Upstream
Commit: 324cc98b71f0d3dee7367ef3c669fd80747e71b6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=324cc98b71f0d3dee7367ef3c669fd80747e71b6
Changed files:
drivers/hid/hid-haptic.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=324cc98b71f0d3dee7367ef3c669fd80747e71b6
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90197 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90197
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:L/PR:N/UI:R/S:U/C:L/I:N/A:N
The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
The Best / paranoid CVSS score: 4.3
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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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