[CVE-2026-98612][MODERATE REGULAR] net: usb: catc: bound the RX packet length in catc_rx_done() [ Upstream

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

CVE: CVE-2026-98612
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: usb: catc: bound the RX packet length in catc_rx_done() [ Upstream
Commit: 3942557938f846e7481f6ccb2b41ccbdee61baa1
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3942557938f846e7481f6ccb2b41ccbdee61baa1
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98612
Analysis date: Sat, 24 Oct 2026 03:52:17 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A malicious CATC USB device can make the receive path copy beyond its URB buffer into an skb, potentially exposing adjacent kernel data or crashing the host.

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

The original Linux kernel CVE announcement for CVE-2026-98612 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98612

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-2026-98612	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98612 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	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-457;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.2';DESCR 'catc_rx_done trusted a packet length relative to the complete URB instead of the bytes remaining after the current packet offset. A malicious or faulty CATC USB device can provide a length that makes skb_copy_to_linear_data read beyond the transfer buffer, while a runt or zero length packet makes eth_type_trans inspect uninitialized skb tailroom. For the CVSS the PR:N value reflects that no authenticated host privilege is required after a hostile USB device is attached, while AV:P reflects the need for physical or equivalent control of the USB device. The concrete primitive is an out of bounds read rather than an out of bounds write or UAF. It may expose adjacent kernel memory through the received skb and may crash the host, but no integrity primitive is established. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.2 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 2 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	MAYBE	USB SIMPLEFIX NETWORK SKB LINUS PACKET  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 2.
* Paranoid score: 2; adds plausible host crash from the invalid source read.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 limited kernel OOB-read primitive: `pkt_len` is checked against the entire URB rather than bytes remaining at `pkt_start`, allowing `skb_copy_to_linear_data()` to read beyond the transfer buffer. Runt packets also cause `eth_type_trans()` to inspect uninitialized skb tailroom.
* +1 firmware/device-mediated attacker influence: a malicious attached CATC USB device controls transfer contents and packet lengths.
* +1 confidentiality plausible: bytes read beyond the URB can be copied into an skb subsequently submitted through `netif_rx()`, providing a technically grounded disclosure path, though actual recoverable data is not demonstrated.
* -2 physical/special-device prerequisite: exploitation requires a malicious or equivalently controlled USB CATC device.
* Paranoid +1 reliable crash/strong DoS concern: an out-of-range source read may fault. This is plausible, not a demonstrated or guaranteed panic.
* No OOB write, UAF, controlled kernel write, authorization bypass, or integrity primitive is shown.
* NEW52/B5-R does not apply: there is no write, retry accumulation, or later consumption of corrupted structured state.
* No separate availability point is awarded for the same possible crash.

3. Reachability analysis

The evidenced attacker is a person controlling an attached physical USB device. No host UID 0, capability, namespace privilege, or authenticated host-administrator action is needed after attachment. Physical access or equivalent device assignment remains mandatory. No race, retry sequence, prior policy setup, or remote-network trigger is shown.

4. Primitive and severity reading

This is a device-controlled OOB source read into an allocated skb, plus an uninitialized-tail read for runt frames. The skb is later consumed by the host network stack, making limited disclosure plausible. It is CLASS_B due to the concrete read-and-forward path, but not an Important candidate: no write, protected-state modification, broad disclosure, or boundary escape is established. Auto-downgrade remains allowed because the primitive is read-only and physically constrained.

5. One-sentence report phrase

A malicious CATC USB device can make the receive path copy beyond its URB buffer into an skb, potentially exposing adjacent kernel data or crashing the host.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm whether captured packets reliably expose out-of-URB bytes and whether the read can cross into faulting memory.

7. Call-site confidence

Call-site confidence: high

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

Patch: net: usb: catc: bound the RX packet length in catc_rx_done() [ Upstream
Commit: 3942557938f846e7481f6ccb2b41ccbdee61baa1
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3942557938f846e7481f6ccb2b41ccbdee61baa1

Changed files:
  drivers/net/usb/catc.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=3942557938f846e7481f6ccb2b41ccbdee61baa1

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

The original Linux kernel CVE announcement for CVE-2026-98612 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98612

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: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).