[CVE-2026-64547][MODERATE REGULAR] net: usb: net1080: validate packet_len before pad-byte access in rx_fixup [ Upstream

[CVE-2026-64547][MODERATE REGULAR] net: usb: net1080: validate packet_len before pad-byte access in rx_fixup [ Upstream

[AL-KERNEL]

CVE: CVE-2026-64547
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: usb: net1080: validate packet_len before pad-byte access in rx_fixup [ Upstream
Commit: f42217fa7d535e9ec4151f7971f06f6ea65e850a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f42217fa7d535e9ec4151f7971f06f6ea65e850a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64547
Analysis date: Wed, 29 Jul 2026 01:21:26 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like, manual review recommended for malicious-device OOB read
Manual review required: YES

Summary:
A malicious NetChip 1080 USB device can advertise a large even packet_len in a short frame, causing net1080_rx_fixup to read past the end of the skb before length validation and potentially crash the kernel.

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

The original Linux kernel CVE announcement for CVE-2026-64547 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64547

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-2026-64547	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:H';CWE-125;*CWE-20;CWE-130;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.2';DESCR 'A malicious NetChip 1080 USB device can advertise a large even packet_len in a short frame. net1080_rx_fixup reads skb data at packet_len before validating that packet_len is inside skb len, so the pad-byte check can perform an out of bounds read in the RX fixup path. For the CVSS the PR:N is used because no host login or local account is needed, only the ability to attach or emulate the USB device. The attack is physical or device-adjacent rather than network reachable over IP. Impact is primarily denial of service when the invalid read hits debugging checks or unsafe memory, and the paranoid score also allows limited confidentiality impact because the primitive is an out of bounds read, although the code path does not show a direct stable information leak channel.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like, manual review recommended for malicious-device OOB read (with actual score 2) 	MAYBE	READ KASAN OOB USB NETWORK SKB HARDWARE PACKET  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like, manual review recommended for malicious-device OOB read**

## 2. Signal breakdown

Conservative signals:

* Device-mediated external influence: +1
  A malicious NetChip 1080 USB device can supply the malformed frame and packet_len value.
* Reliable kernel crash / strong DoS: +1
  The report shows a KASAN slab-out-of-bounds read in net1080_rx_fixup. On production kernels, this may be less reliably fatal, but the bug is in kernel RX processing and can plausibly crash hardened or debug builds.
* Availability impact realistic: +1
  If the invalid read faults or triggers a fatal sanitizer or hardening check, the impact is host kernel DoS.
* Physical-only or rare hardware-only condition: -2
  The attacker needs physical access or an emulated malicious USB device. This is not IP-network reachable.

Paranoid additional signal:

* Confidentiality impact plausible: +1
  The primitive is an out-of-bounds read, so limited C impact is technically defensible. However, the byte is only compared against PAD_BYTE and there is no clear user-visible disclosure channel.

Not awarded:

* No generic strong memory corruption bonus. This is read-only OOB, not OOB write, UAF, double free, or type confusion.
* No privilege escalation bonus. The patch does not show reclaim, overwrite, callback control, refcount abuse, or attacker-controlled object replacement.
* No remote/network-triggerable bonus. The affected path is USB device input, not remote packet input over IP.

## 3. Reachability analysis

The bug can be triggered by a malicious or emulated NetChip 1080 USB device that sends a short frame while advertising a large even packet_len. No local account on the host is required, but physical or device-level access is required. Namespaces and containers do not materially lower the privilege requirement because the trigger is attachment or emulation of the USB device, not a normal unprivileged local syscall or network socket. The affected driver is device-specific and not a broad default network receive path for ordinary Ethernet or IP traffic.

Call-site confidence: high. The provided context shows the vulnerable dereference in net1080_rx_fixup and the USB networking RX path through usbnet_bh.

## 4. Severity interpretation

This behaves more like an ordinary Moderate or Low-like hardware-adjacent issue than an Important kernel vulnerability. The theoretical memory-safety concern is a limited out-of-bounds read, but the realistic impact is mainly crash or sanitizer-triggered DoS from a malicious USB device. There is no demonstrated information disclosure path and no practical privilege escalation primitive in the patch context.

## 5. One-sentence report phrase

A malicious NetChip 1080 USB device can advertise a large even packet_len in a short frame, causing net1080_rx_fixup to read past the end of the skb before length validation and potentially crash the kernel.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is a malicious-device-triggered kernel out-of-bounds read, so it should not be dismissed purely as cosmetic, but the physical-only reachability and lack of write, UAF, disclosure, or LPE primitive keep it below Actionable Moderate / Important handling.

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

Patch: net: usb: net1080: validate packet_len before pad-byte access in rx_fixup [ Upstream
Commit: f42217fa7d535e9ec4151f7971f06f6ea65e850a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f42217fa7d535e9ec4151f7971f06f6ea65e850a

Changed files:
  drivers/net/usb/net1080.c
  drivers/net/usb/usbnet.c
  kernel/workqueue.c
  kernel/softirq.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=f42217fa7d535e9ec4151f7971f06f6ea65e850a

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

The original Linux kernel CVE announcement for CVE-2026-64547 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64547

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:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 5.2

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).