[CVE-2026-46167][LOW] usb: usblp: fix uninitialized heap leak via LPGETSTATUS ioctl

[CVE-2026-46167][LOW] usb: usblp: fix uninitialized heap leak via LPGETSTATUS ioctl

[AL-KERNEL]

CVE: CVE-2026-46167
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: usb: usblp: fix uninitialized heap leak via LPGETSTATUS ioctl
Commit: d06d937b0a4cdb8867f04275c8100a8b943da31a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d06d937b0a4cdb8867f04275c8100a8b943da31a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46167
Analysis date: Thu, 28 May 2026 11:19:34 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
`usblp` could expose one stale kernel heap byte through `LPGETSTATUS` when a malformed USB printer returned zero bytes before the status buffer had been initialized.

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

The original Linux kernel CVE announcement for CVE-2026-46167 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46167

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-2026-46167	LOW	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N';*CWE-457;*CWE-200;CWE-908;CWE-665;Other CVSS 'AV:P/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '2.5';DESCR 'usblp allocated the printer status buffer with kmalloc and did not initialize it before the first LPGETSTATUS ioctl. If a malformed USB printer returns zero bytes for the one byte status request, the ioctl can copy a stale heap byte to userspace after sign extension into an int. For the CVSS the PR:L is used for the paranoid score because a local user needs access to the usblp device node or an equivalent USB passthrough context. The main attack model is physical or local device access, not network reachability. Impact is limited kernel information disclosure only, with no supported memory corruption, write primitive, or privilege escalation path.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) 	MAYBE	USB LEAK HARDWARE LINUS 	-	-	checked

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

ActionableScore=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Positive signals:

* Confidentiality impact plausible: +1. `LPGETSTATUS` may copy one stale heap byte to userspace if the status buffer was never initialized.
* Local user/device access trigger: +1. A local user needs access to the `usblp` device node and the malformed printer behavior.

Negative / limiting signals:

* Physical or local USB-device condition: -2. The main attacker model requires a malicious USB printer or USB passthrough context.
* No memory corruption. This is an uninitialized heap byte disclosure, not UAF, OOB write, double free, or arbitrary write.
* No privilege escalation.
* No network reachability.
* Very constrained leak size. The directly described leak is one stale byte through a status ioctl.

## 3. Reachability analysis

The issue is triggered when a malformed USB printer returns zero bytes for a one-byte status request and a local process calls `LPGETSTATUS`. The attacker generally needs physical USB device control, USB passthrough, or control of the attached printer.

A local unprivileged user may only exploit it if they can open the `usblp` device node. Containers matter only if USB printer passthrough or the `usblp` node is delegated into the container.

## 4. Severity interpretation

This behaves like Low / ordinary Moderate. The realistic impact is a very small kernel heap information disclosure to a local ioctl caller.

There is no supported memory corruption, integrity impact, availability impact, or privilege escalation path.

## 5. One-sentence report phrase

`usblp` could expose one stale kernel heap byte through `LPGETSTATUS` when a malformed USB printer returned zero bytes before the status buffer had been initialized.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can generally be auto-closed for urgent security triage because it is a tiny physical/local USB information leak with no memory corruption or LPE evidence.

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

Patch: usb: usblp: fix uninitialized heap leak via LPGETSTATUS ioctl
Commit: d06d937b0a4cdb8867f04275c8100a8b943da31a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d06d937b0a4cdb8867f04275c8100a8b943da31a

Commit description:

Just like in a previous problem in this driver, usblp_ctrl_msg() will
collapse the usb_control_msg() return value to 0/-errno, discarding the
actual number of bytes transferred.

Ideally that short command should be detected and error out, but many
printers are known to send "incorrect" responses back so we can't just
do that.

statusbuf is kmalloc(8) at probe time and never filled before the first
LPGETSTATUS ioctl.

usblp_read_status() requests 1 byte. If a malicious printer responds
with zero bytes, *statusbuf is one byte of stale kmalloc heap,
sign-extended into the local int status, which the LPGETSTATUS path then
copy_to_user()s directly to the ioctl caller.

Fix this all by just zapping out the memory buffer when allocated at
probe time.  If a later call does a short read, the data will be
identical to what the device sent it the last time, so there is no
"leak" of information happening.

Cc: Pete Zaitcev <zaitcev@redhat.com>
Assisted-by: gkh_clanker_t1000
Cc: stable <stable@kernel.org>
Link: https://patch.msgid.link/2026042011-shredder-savage-48c6@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/usb/class/usblp.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=d06d937b0a4cdb8867f04275c8100a8b943da31a

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

The original Linux kernel CVE announcement for CVE-2026-46167 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46167

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:L/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS score: 2.5

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: unknown
  Paranoid ActionableScore: 1

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