* [CVE-2026-90402][LOW] bus: mhi: host: Fix controller cleanup on EDL sysfs failure [ Upstream
@ 2026-09-18 11:48 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-18 11:48 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-90402
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: bus: mhi: host: Fix controller cleanup on EDL sysfs failure [ Upstream
Commit: 7943dc67250fad6ceac0dd089c6ad5776e4be71d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7943dc67250fad6ceac0dd089c6ad5776e4be71d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90402
Analysis date: Fri, 18 Sep 2026 07:48:46 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90402 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90402
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.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-90402 LOW https://www.kernelcve.org/list/?q=CVE-2026-90402 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-404;CWE-755;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.1';DESCR 'MHI controller registration adds the controller device before creating the optional trigger_edl sysfs file. If sysfs_create_file() fails, the old error path only called put_device() and could leave an already registered device in the device model instead of fully unregistering it. For the CVSS the PR:H is used because reliable triggering normally requires privileged driver or platform control over MHI controller registration and the failure path. The issue is not network reachable. Impact is limited to availability through incomplete cleanup, leaked device state, or possible sysfs and device model inconsistency. No memory corruption or privilege escalation primitive is indicated by this patch.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) YES SIMPLEFIX ERRORPATH HARDWARE LINUS YES NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: -1
* Conservative score: 0
* Raw paranoid score: -1
* Paranoid score: 0
* Applied conservative floor/cap: raw -1 clamped to 0 because ActionableScore lower bound is 0.
* Applied paranoid floor/cap: raw -1 clamped to 0 because ActionableScore lower bound is 0.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
Positive signals:
* +1 Concrete persistent kernel resource/reference leak. The patch directly establishes that after the controller device is added, failure of sysfs_create_file() leaves the device registered because the old error path only called put_device() and skipped device_del().
* +0 Reliable kernel crash / strong DoS not awarded. No panic, UAF, Oops, double free, or host-wide fatal fault is shown.
* +0 Confidentiality and integrity not awarded. The patch shows incomplete cleanup only, not disclosure, unauthorized modification, or security-boundary bypass.
* +0 Strong exploitation leverage not awarded. No controlled reclaim, arbitrary write, refcount takeover, callback influence, or LPE path is established.
Negative signals:
* -2 Host-admin-equivalent control required. The vulnerable path is mhi_register_controller(), which is reached through MHI controller driver/platform registration, not an ordinary user interface.
* +0 Race penalty not applied. This is an ordered error-path cleanup bug, not a timing race.
* +0 Rare hardware penalty not applied separately. The MHI subsystem is hardware related, but the host-admin registration requirement already captures the practical reachability limitation.
Important non-awarded signals:
* Real UAF not established.
* Concrete repeated release/refcount mutation not established.
* Controlled reclaim not demonstrated.
* Arbitrary read/write not demonstrated.
* Remote reachability not established.
* Extra availability not awarded because only a potential cleanup/resource leak is shown.
3. Reachability analysis
The complete trigger requires entering MHI controller registration and then hitting the sysfs_create_file() failure path for the optional trigger_edl file. This is normally controlled by kernel driver or platform/device-management activity, not by an ordinary local user.
HostAdminRequired=YES because reliable triggering requires host-admin-equivalent driver/platform control or fault-injection style control over the registration failure path. NamespaceScopedPrivilege=NO because there is no evidence that this MHI controller registration operation is reachable through an attacker-created namespace or namespace-scoped capability.
No direct network trigger is present. No prior attacker-obtainable runtime object is shown. No race repeatability or ordinary unprivileged loop is established.
4. Primitive and severity interpretation
The exact primitive is incomplete device-model cleanup after partial registration. The controller device can remain registered if creating the optional sysfs EDL attribute fails and the error path skips device_del().
This is not an active structured UAF and not fixed stale storage with post-free access. It is a device lifecycle/resource cleanup inconsistency. There is no concrete repeated release/refcount operation because the bug is missing device_del() before put_device(), not a second put/free through a dangling reference.
PrimitiveClass=CLASS_C because the demonstrated behavior is invalid cleanup/resource state without an independently useful corruption primitive. Demonstrated consequence is a leaked or inconsistent registered device state. Speculative consequence is limited availability degradation if the failure can be repeated, but the supplied evidence does not establish host-wide exhaustion or exploitation leverage.
ImportantCandidate=NO because there is no memory corruption, authorization bypass, COW/ownership violation, UAF, or below-host-admin reachable security primitive. AutoDowngradeAllowed=YES because the issue is constrained to privileged cleanup/error handling and no unresolved Important-grade primitive remains.
Likely operational severity is Low-like to ordinary Moderate.
5. One-sentence report phrase
MHI controller registration could leave a controller device registered after trigger_edl sysfs file creation failed, causing incomplete cleanup and a possible device-model resource leak, but reliable triggering requires host-admin-level driver or platform control and no memory corruption or privilege escalation primitive is shown.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
Reason: this is a privileged error-path cleanup/resource leak with no UAF, no repeated lifetime mutation, no boundary bypass, no remote reachability, and no demonstrated host-wide crash or exploitation primitive.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: bus: mhi: host: Fix controller cleanup on EDL sysfs failure [ Upstream
Commit: 7943dc67250fad6ceac0dd089c6ad5776e4be71d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7943dc67250fad6ceac0dd089c6ad5776e4be71d
Changed files:
drivers/bus/mhi/host/init.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=7943dc67250fad6ceac0dd089c6ad5776e4be71d
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90402 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90402
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:H/PR:H/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.1
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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