[CVE-2026-90025][MODERATE REGULAR] usb: typec: ucsi: displayport: Fix OOB altmode array index

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

CVE: CVE-2026-90025
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: usb: typec: ucsi: displayport: Fix OOB altmode array index
Commit: 8fde7e4a366184e9a6aa95541e52933a73c00a74
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8fde7e4a366184e9a6aa95541e52933a73c00a74
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90025
Analysis date: Wed, 16 Sep 2026 12:53:44 -0400
ActionableScore: 3
ActionableScore lower bound: 2
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-2026-90025 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90025

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-2026-90025	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90025 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';CWE-129;CWE-125;*CWE-20;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.7';DESCR 'An out of bounds array access in the UCSI DisplayPort alt mode path can occur because the GET_CURRENT_CAM response is used as an index into the connector port_altmode array after checking only for the special 0xff value. If the PPM returns a value greater than or equal to UCSI_MAX_ALTMODES and not 0xff, the kernel may read outside the port_altmode array and crash. For the CVSS the PR:N is used because the selected paranoid interpretation assumes an attacker controlled or attacker influenced Type C device or PPM response and no local account on the host. The issue is not network reachable and requires physical or platform specific Type C exposure. Impact is at least denial of service via kernel crash. Worst case is kept below high severity because the patch shows an OOB read style array access, not an OOB write or clear arbitrary memory corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	YES	OOB DANGER USB SIMPLEFIX KERNEL_PANIC_PLUS_UAF LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	NO	NO	checked

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

ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline / manual review recommended**::

No floor or cap was applied.

2. Signal breakdown

Conservative positive signals:

* +1 Weak / indirect corruption candidate: unchecked GET_CURRENT_CAM value is used as an index into the `port_altmode` array.
* +1 Reliable kernel crash / strong DoS: commit states the kernel may crash with an OOB array index error.

Paranoid additional signal:

* +1 Firmware-mediated external influence: a malicious or malformed Type C / UCSI PPM response may influence the invalid CAM value, but this is mediated by platform firmware/controller behavior rather than direct network input.

Negative signals:

* No -2 host-admin penalty: host-admin-equivalent privilege is not positively established.
* No -2 physical-only penalty: physical or platform-specific Type C exposure is relevant, but USB Type C / UCSI is not inherently rare hardware.
* No -1 race penalty: no race or timing dependency is involved.

Important non-awarded signals:

* RealUAF not awarded: no stale lifetime use or use-after-free is shown.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Confidentiality not awarded: the OOB read is internal and no disclosure path is shown.
* Integrity not awarded: the patch shows array over-index read/compare, not a write or state corruption primitive.
* Remote reachability not established.
* Extra Availability not awarded because the crash is already counted once.

3. Reachability analysis

The vulnerable value comes from the UCSI GET_CURRENT_CAM response. A practical attacker model is therefore a malformed or attacker-influenced Type C / UCSI environment, such as a problematic PPM response or a device/platform path that can cause such a response. The issue is not network reachable.

Host administrator privilege is not shown as a required condition, but the complete attacker-controlled path from an external Type C device to an invalid PPM response is not fully established by the patch alone. Therefore HostAdminRequired is UNKNOWN rather than YES or NO.

No namespace-scoped privilege is relevant. There is no CAP_NET_ADMIN, container, netns, BPF, KVM, ptrace, or filesystem ownership boundary in the supplied patch. Prior host setup is mainly the presence of UCSI DisplayPort alt mode support on the platform. No race repeatability issue exists.

4. Primitive and severity interpretation

The exact primitive is an unchecked array index into `dp->con->port_altmode[cur]` where `cur` can be greater than or equal to `UCSI_MAX_ALTMODES` and not equal to `0xff`. This is best classified as a limited OOB read / invalid pointer-array access in kernel code.

This is not an active structured UAF and not fixed stale storage. There is no concrete repeated release/refcount operation. There is no first lifetime operation that may free an object and no second lifetime mutation through a dangling reference.

PrimitiveClass is CLASS_C because the demonstrated behavior is crash/DoS from invalid OOB access without an independently useful corruption primitive. Demonstrated consequence is kernel crash. Speculative consequence would require an additional disclosure, write, or control-flow primitive that is not supported here.

ImportantCandidate is NO because the patch does not establish UAF, OOB write, controlled replacement, authorization bypass, or meaningful C/I impact. AutoDowngradeAllowed is YES because this is a constrained crash-oriented OOB access, though manual review is still recommended due to kernel OOB indexing and hardware-mediated reachability uncertainty.

Likely operational severity is low-to-borderline moderate, mainly physical/platform-local DoS.

5. One-sentence report phrase

A malformed UCSI DisplayPort GET_CURRENT_CAM response can cause an out-of-bounds port_altmode array access and kernel crash, with no network reachability and no demonstrated privilege escalation or data disclosure.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: kernel OOB array indexing is concrete, but the demonstrated impact is DoS only and the attacker-controlled Type C / PPM reachability needs platform-specific validation.

7. Call-site confidence

Call-site confidence: high

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

Patch: usb: typec: ucsi: displayport: Fix OOB altmode array index
Commit: 8fde7e4a366184e9a6aa95541e52933a73c00a74
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8fde7e4a366184e9a6aa95541e52933a73c00a74

Commit description:

The UCSI displayport driver indexes the connector's port altmode array
with the GET_CURRENT_CAM response after checking it is not 0xff. The
port altmode array is UCSI_MAX_ALTMODES elements long. If the PPM
returns an invalid GET_CURRENT_CAM response above UCSI_MAX_ALTMODES and
not equal to 0xff, the kernel may crash with an array index OOB error.

Update the UCSI displayport driver to verify the current cam is less
than UCSI_MAX_ALTMODES before accessing the port altmode array.

Fixes: af8622f ("usb: typec: ucsi: Support for DisplayPort alt mode")
Cc: stable@vger.kernel.org
Signed-off-by: Jameson Thies <jthies@google.com>
Reviewed-by: Benson Leung <bleung@chromium.org>
Link: https://patch.msgid.link/20260825234545.2076049-1-jthies@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/usb/typec/ucsi/displayport.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=8fde7e4a366184e9a6aa95541e52933a73c00a74

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

The original Linux kernel CVE announcement for CVE-2026-90025 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90025

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:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.7

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: 2
  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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).