[CVE-2026-89628][MODERATE REGULAR] HID: picolcd: clamp eeprom debugfs read to bytes actually received

[CVE-2026-89628][MODERATE REGULAR] HID: picolcd: clamp eeprom debugfs read to bytes actually received

[AL-KERNEL]

CVE: CVE-2026-89628
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: HID: picolcd: clamp eeprom debugfs read to bytes actually received
Commit: a3e6e8d7198a9f3861861520a38b673684a1062b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a3e6e8d7198a9f3861861520a38b673684a1062b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89628
Analysis date: Sat, 12 Sep 2026 04:02:56 -0400
ActionableScore: 2
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-2026-89628 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89628

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-89628	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-89628 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:L';CWE-125;CWE-126;*CWE-20;*CWE-200;Other CVSS 'AV:P/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '4.6';DESCR 'A kernel slab out-of-bounds read in the HID PicoLCD debugfs eeprom path can occur because picolcd_debug_eeprom_read() trusts a device supplied length byte without also checking the number of bytes actually received. A crafted or spoofed PicoLCD HID device can report an excessive EEPROM payload length and make copy_to_user() read past the 64 byte raw_data buffer into adjacent slab memory. For the CVSS the PR:H is used because the debugfs eeprom file is root-only in the normal configuration. The issue is not network reachable and also requires a malicious or spoofed local HID device. Impact is primarily information disclosure of adjacent kernel memory to a privileged local reader. Availability impact is only secondary, for example under debug or hardened builds that turn the out-of-bounds read into a report or crash.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	READ KASAN OOB USB HARDWARE DEBUGFS LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	NO	NO	checked

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

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

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2. No floor or cap applied.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1. Concrete bounded kernel OOB read exists. `picolcd_debug_eeprom_read()` can copy beyond `resp->raw_data[]` because it trusts a device supplied length byte without checking `resp->raw_size`.
* +1. User-visible disclosure path exists. The overread bytes are returned through `copy_to_user()` to the reader of the debugfs `eeprom` file.
* +1. Firmware or device mediated external influence exists. A hostile or spoofed PicoLCD HID device can supply the excessive length byte.

Negative signals:

* -2. Host-admin-equivalent privilege is positively established. The affected debugfs file is created as `S_IRUSR`, i.e. root-only in the normal configuration.

Important non-awarded signals:

* No UAF or lifetime violation is established.
* No write primitive is established.
* No controlled reclaim or object replacement is established.
* No privilege escalation path is established.
* No remote reachability is established.
* No reliable production kernel crash is scored. The KASAN report demonstrates the OOB read, but the primary consequence is disclosure to a privileged reader.
* No extra availability point is awarded because availability impact is secondary and not independently demonstrated for normal production systems.

3. Reachability analysis

The complete trigger requires a crafted or spoofed local PicoLCD HID device and a privileged local reader able to access the root-only debugfs `eeprom` file. This is not reachable by an ordinary unprivileged local user based on the supplied evidence. It is not namespace-scoped. There is no network trigger. The device requirement is material, but the stronger concrete reducing condition is the root-only debugfs access, so the score is driven mainly by host-admin reachability rather than by public attacker exposure.

4. Primitive and severity interpretation

The exact primitive is a bounded slab out-of-bounds read from adjacent kernel memory followed by `copy_to_user()`. This is not an active structured UAF, not fixed stale storage, and not a repeated release or refcount mutation. The demonstrated consequence is limited information disclosure to a privileged local reader. A malicious device can influence the length field, but the leaked bytes go to the root-only debugfs reader, not directly back to a remote attacker or ordinary local user. Therefore this remains CLASS_C for actionable triage and is not an Important candidate.

ImportantCandidate=NO because the issue lacks UAF, write corruption, authorization bypass, low-privilege reachability, or a demonstrated privilege escalation chain.

AutoDowngradeAllowed=YES because the established primitive is constrained, root-only, device-mediated, and does not leave unresolved Important-grade exploitation leverage.

5. One-sentence report phrase

A crafted PicoLCD HID device can cause a root-only debugfs EEPROM read to copy beyond the received 64 byte response buffer and disclose adjacent kernel slab memory to the privileged reader.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is a real kernel OOB read with a disclosure path, but the affected interface is root-only and requires a crafted local HID device, so it is suitable for non-urgent triage rather than automatic Important handling.

7. Call-site confidence

Call-site confidence: high

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

Patch: HID: picolcd: clamp eeprom debugfs read to bytes actually received
Commit: a3e6e8d7198a9f3861861520a38b673684a1062b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a3e6e8d7198a9f3861861520a38b673684a1062b

Commit description:

picolcd_debug_eeprom_read() trusts resp->raw_data[2] -- a length byte
supplied by the device in its REPORT_EE_DATA reply -- clamped only to
the caller's read() count:

	ret = resp->raw_data[2];
	if (ret > s)
		ret = s;
	if (copy_to_user(u, resp->raw_data+3, ret))

It never checks resp->raw_size, the number of bytes picolcd_raw_event()
actually copied into the 64-byte raw_data[] of the kmalloc'd struct
picolcd_pending. A device (or a spoofed picoLCD) returning a length byte
of 0xff, read with a count >= 255, makes copy_to_user() read past
raw_data[] into adjacent slab memory and return it to userspace through
the debugfs "eeprom" file:

	BUG: KASAN: slab-out-of-bounds in _copy_to_user
	Read of size 255 ... picolcd_debug_eeprom_read+0x214/0x2f0 [hid_picolcd]

The debug-dump path in the same file already validates the device length
byte against the received size before trusting it; this read does not.
The file is created S_IRUSR (root-only) and a crafted device is needed,
so it is neither unprivileged- nor remotely-triggerable.

Clamp the copy length to resp->raw_size - 3 (the payload actually
received, minus the 3-byte header), floored at 0 for short replies.

Fixes: 9bbf2b9 ("HID: add experimental access to PicoLCD device's EEPROM and FLASH")
Cc: stable@vger.kernel.org
Signed-off-by: Ibrahim Hashimov <security@auditcode.ai>
Assisted-by: AuditCode-AI:2026.07
Signed-off-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/hid/hid-picolcd_debugfs.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=a3e6e8d7198a9f3861861520a38b673684a1062b

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

The original Linux kernel CVE announcement for CVE-2026-89628 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89628

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:H/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:L
  The Best / paranoid CVSS score: 4.6

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: 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).