[CVE-2026-80814][MODERATE REGULAR] rndis_host: add overflow check in rndis_rx_fixup()

[CVE-2026-80814][MODERATE REGULAR] rndis_host: add overflow check in rndis_rx_fixup()

[AL-KERNEL]

CVE: CVE-2026-80814
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: rndis_host: add overflow check in rndis_rx_fixup()
Commit: 2140db1232af04b92faa6c4a2a40df6371ea89ff
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2140db1232af04b92faa6c4a2a40df6371ea89ff
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80814
Analysis date: Fri, 04 Sep 2026 13:19:24 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A malicious USB RNDIS device can craft packet metadata that causes integer wraparound in `rndis_rx_fixup()`, bypassing bounds validation and enabling an OOB read of the USB data buffer with possible limited information exposure or kernel crash DoS.

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

The original Linux kernel CVE announcement for CVE-2026-80814 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80814

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-2026-80814	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80814 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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-190;CWE-125;*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 'An integer overflow in rndis_rx_fixup can let a malformed RNDIS packet bypass the data_offset plus data_len plus 8 bounds check and cause an OOB read from the USB data buffer. A malicious USB RNDIS device can trigger this by sending crafted packet metadata with wrapping length arithmetic. For the CVSS the PR:N because no account or local privileges are needed once the attacker controls the attached USB RNDIS device. The issue is not directly reachable from the IP network or the public Internet and normally requires physical or USB level access to the target. Impact is mainly denial of service and possible limited confidentiality exposure from an out of bounds read, with no clear evidence of an OOB write or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 2)	YES	OOB USB SIMPLEFIX NETWORK LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Device-mediated external influence: +1. A malicious USB RNDIS device controls the RNDIS packet metadata consumed by `rndis_rx_fixup()`.
* Confidentiality impact plausible: +1. The bug enables an OOB read of the USB data buffer, but no user-visible disclosure path is demonstrated.
* Physical-only or rare hardware-only condition: -2. Practical triggering requires an attached malicious or compromised USB RNDIS device, not ordinary remote IP traffic.

Paranoid additional signals:

* Reliable kernel crash / strong DoS: +1. An OOB read in a kernel network receive path can plausibly lead to a kernel fault depending on skb layout and surrounding memory.
* Common driver/protocol exposure: +1. RNDIS USB networking is a common USB network class, especially for tethering, docks, gadgets, and embedded devices.

Not awarded:

* No remote reachable / network-triggerable +2. This is not reachable from the public IP network.
* No strong memory corruption +2. The patch supports OOB read, not OOB write, UAF, double-free, or controlled overwrite.
* No privilege escalation plausible +2. There is no demonstrated write primitive, object replacement, callback control, or reclaim path.

## 3. Reachability analysis

The realistic attacker is a malicious USB RNDIS peripheral, USB gadget, dock, or compromised device presenting itself as an RNDIS network adapter. No local account is needed once the attacker controls the attached USB device, but physical or USB-level access is normally required. Namespaces and containers do not materially lower the requirement because the vulnerable parsing occurs in the host kernel driver when the USB network device receives frames. The path is enabled only when the `rndis_host` driver is used for an attached RNDIS device.

## 4. Severity interpretation

This behaves like an ordinary Moderate to borderline actionable Moderate issue. The primitive is an integer overflow leading to an OOB read from an skb/USB data buffer. The realistic impact is limited confidentiality exposure or kernel crash DoS. Theoretical escalation is not supported by the patch because there is no OOB write, lifetime corruption, type confusion, or attacker-controlled kernel object reuse.

## 5. One-sentence report phrase

A malicious USB RNDIS device can craft packet metadata that causes integer wraparound in `rndis_rx_fixup()`, bypassing bounds validation and enabling an OOB read of the USB data buffer with possible limited information exposure or kernel crash DoS.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the issue is externally attacker-influenced through a USB network receive path and involves an OOB read in kernel parsing code, but it should not be treated as Important without additional evidence of disclosure, write corruption, or privilege escalation.

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

Patch: rndis_host: add overflow check in rndis_rx_fixup()
Commit: 2140db1232af04b92faa6c4a2a40df6371ea89ff
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2140db1232af04b92faa6c4a2a40df6371ea89ff

Commit description:

Add an overflow check to ensure that data_offset + data_len + 8 does not
wrap, which would enable an OOB read of the USB data buffer.

Cc: Andrew Lunn <andrew+netdev@lunn.ch>
Cc: Shaoxu Liu <shaoxul@foxmail.com>
Signed-off-by: Griffin Kroah-Hartman <griffin@kroah.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/2026070900-denim-brook-52d4@gregkh
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/usb/rndis_host.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=2140db1232af04b92faa6c4a2a40df6371ea89ff

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

The original Linux kernel CVE announcement for CVE-2026-80814 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80814

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: 3

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).