[CVE-2026-63963][MODERATE REGULAR] usb: typec: tcpm: validate VDO count in Discover Identity ACK handlers

[CVE-2026-63963][MODERATE REGULAR] usb: typec: tcpm: validate VDO count in Discover Identity ACK handlers

[AL-KERNEL]

CVE: CVE-2026-63963
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: usb: typec: tcpm: validate VDO count in Discover Identity ACK handlers
Commit: 569f7971542eb10025d8a0989b83f28a29d8ba20
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=569f7971542eb10025d8a0989b83f28a29d8ba20
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63963
Analysis date: Sun, 19 Jul 2026 18:30:16 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like, but manual review recommended for information-leak correctness
Manual review required: YES

Summary:
A malicious USB Type-C / USB PD device can provide an invalid Discover Identity VDO count that may cause the TCPM identity handlers to read beyond valid identity data and leak limited kernel or driver state, with no network reachability and no evidence of privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-63963 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63963

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-2026-63963	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	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:N/A:L';CWE-125;*CWE-20;*CWE-200;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '3.5';DESCR 'A USB Type-C TCPM Discover Identity ACK handler can consume a device controlled VDO count without enough validation, allowing a malicious USB PD partner or cable to drive out-of-bounds reads from identity data arrays. The likely impact is a limited information leak from kernel or driver state associated with Type-C identity handling, not a direct write primitive or use-after-free. For the CVSS the PR:N because the malformed identity response is supplied by the connected device and no local host privileges are required after physical connection. The issue is not network reachable and requires physical access or a malicious accessory connected to the target system. Impact is mainly confidentiality loss with possible low availability impact in the paranoid score, but no supported path to privilege escalation is visible from this patch.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like, but manual review recommended for information-leak correctness (with actual score 2)	YES	REMOTE USB SIMPLEFIX LEAK NETWORK HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: **1**
* Paranoid score: **2**
* Final recommended bucket: **Ordinary Moderate / Low-like, but manual review recommended for information-leak correctness**::

## 2. Signal breakdown

Triggered signals:

* **Firmware/device-mediated external influence: +1**
  The VDO count is controlled by an attached USB Type-C / USB PD partner, cable, or accessory.

* **Confidentiality impact plausible: +1**
  The commit explicitly says the device-controlled count could index off static arrays and leak data. This supports limited information disclosure.

* **Broad/common hardware exposure: +1**
  USB Type-C TCPM is a common kernel subsystem on laptops, phones, docks, and embedded systems with USB-C PD support.

Subtracted signals:

* **Physical-only or rare hardware-only condition: -2**
  Exploitation requires a malicious physical USB-C / USB PD device, cable, dock, or accessory connected to the target. There is no network path.

Paranoid-only signal:

* **Low availability impact plausible: +1**
  A malformed identity response might disrupt Type-C / PD identity handling or cable discovery, but the patch does not show a reliable kernel crash.

Not counted:

* **No generic memory corruption bonus**
  This is an out-of-bounds read / info leak candidate, not an OOB write, UAF, double-free, or type confusion.

* **No privilege escalation bonus**
  The patch does not show attacker-controlled write, reclaim, callback control, refcount abuse, or another LPE primitive.

## 3. Reachability analysis

A malicious USB Type-C / USB PD partner can trigger the path by returning a malformed Discover Identity ACK with an invalid VDO count. No local user privileges are required on the host after the physical connection is made, but the attacker needs physical access or control over an attached accessory. Namespaces and containers do not materially affect reachability because the trigger is external hardware protocol input, not a local userspace API. The path is relevant only on systems using TCPM-managed USB-C / PD ports.

Call-site confidence: **high**, because the changed handlers and the relevant indexed accesses are visible in the patch.

## 4. Severity interpretation

This behaves more like **Low / ordinary Moderate** than Important. The realistic impact is limited information disclosure from kernel or driver identity-handling state through a physical-device attack surface. The theoretical worst case includes minor availability disruption, but there is no evidence of write corruption, UAF, privilege escalation, or remote reachability.

One important manual-review point is that the shown diff initializes `vdo` and `product` from `p[...]` before the newly added `cnt` checks. If that reflects the final compiled source exactly and `p` can truly be shorter than those indexes, the fix ordering should be checked.

## 5. One-sentence report phrase

A malicious USB Type-C / USB PD device can provide an invalid Discover Identity VDO count that may cause the TCPM identity handlers to read beyond valid identity data and leak limited kernel or driver state, with no network reachability and no evidence of privilege escalation.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED**

Reason: the bug is a device-controlled kernel out-of-bounds read / information-leak candidate, and the visible patch appears to add count checks after some indexed reads are already performed, so the final source context should be verified manually.

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

Patch: usb: typec: tcpm: validate VDO count in Discover Identity ACK handlers
Commit: 569f7971542eb10025d8a0989b83f28a29d8ba20
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=569f7971542eb10025d8a0989b83f28a29d8ba20

Commit description:

Properly validate the count passed from a device when calling
svdm_consume_identity() or svdm_consume_identity_sop_prime() as the
device-controlled value could index off of the static arrays, which
could leak data.

Assisted-by: gkh_clanker_t1000
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: stable <stable@kernel.org>
Reviewed-by: Badhri Jagan Sridharan <badhri@google.com>
Link: https://patch.msgid.link/2026051350-plated-salute-0efe@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/usb/typec/tcpm/tcpm.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=569f7971542eb10025d8a0989b83f28a29d8ba20

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

The original Linux kernel CVE announcement for CVE-2026-63963 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63963

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:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
  The Best / paranoid CVSS score: 3.5

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: 1
  Paranoid ActionableScore: 2

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).