[CVE-2026-68365][MODERATE 7.0] USB: serial: io_edgeport: cap received transmit credits

[CVE-2026-68365][MODERATE 7.0] USB: serial: io_edgeport: cap received transmit credits

[AL-KERNEL]

CVE: CVE-2026-68365
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: USB: serial: io_edgeport: cap received transmit credits
Commit: ee57992c053a6d395e98ced2d4c9cc3b42d8c27a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee57992c053a6d395e98ced2d4c9cc3b42d8c27a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68365
Analysis date: Mon, 10 Aug 2026 11:03:35 -0400
ActionableScore: 6
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A malicious or non-conforming USB Edgeport-compatible serial device can report excessive transmit credits, causing txCredits to exceed maxTxCredits and allowing edge_write to write beyond the allocated TX FIFO ring buffer, resulting in kernel memory corruption with at least DoS impact and possible privilege escalation.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-68365 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68365

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 7.0
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-2026-68365	MODERATE	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:H/I:H/A:H';*CWE-787;*CWE-20;CWE-682;Other CVSS 'AV:P/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H';BEST CVSS score: '6.8';DESCR 'A kernel out of bounds write can occur in the USB serial io_edgeport driver because transmit credits reported by the device are accumulated without being capped at maxTxCredits. edge_write uses txCredits to decide how much data fits in the software FIFO, while the FIFO is allocated with maxTxCredits bytes. A malicious or non conforming USB Edgeport compatible device can therefore report excessive credits and make the driver write beyond the TX ring buffer. For the CVSS the PR:N is used because the attacking device does not need an account or local user privileges on the target system. The attack is not network reachable and normally requires physical access or a victim attaching the device. Impact is at least denial of service via kernel crash and may include privilege escalation because the primitive is an out of bounds write in kernel memory. For the paranoid score, the highest still defensible interpretation is used because the bug class is kernel memory corruption rather than a DoS only logic error.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	WRITE OOB USB PRINTF-TTY SIMPLEFIX HARDWARE LINUS KPANIC PACKET  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=6
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 6
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Firmware-mediated or device-mediated external influence: +1. The malformed transmit credits come from the USB device via interrupt-status packets.
* Generic memory corruption, strong primitive: +2. The commit explicitly states that excessive txCredits can cause an OOB write in the ring buffer.
* Reliable kernel crash / strong DoS: +1. An OOB write in a kernel driver transmit FIFO is a realistic crash primitive.
* Privileged kernel/device-management memory corruption path: +1. The corruption occurs inside a trusted USB serial kernel driver path fed by device-reported state.
* Physical-only or rare hardware-only condition: -2. Practical triggering requires a malicious or non-conforming USB Edgeport-compatible device or equivalent physical/device access.

Paranoid additional interpretation:

* Privilege escalation plausible: +1. The primitive is an OOB write in kernel memory, so LPE cannot be excluded, but no controlled target, reclaim, function pointer, or arbitrary write primitive is demonstrated.
* Confidentiality impact plausible: +1. Possible only as a consequence of kernel memory corruption, not directly shown.
* Integrity impact plausible: +1. Possible because this is a write past a kernel ring buffer boundary.
* Constrained primitive concern: -1. The overwrite appears tied to a driver-local TX FIFO/ring-buffer path, with limited evidence of attacker-controlled target selection.

## 3. Reachability analysis

The likely attacker is a malicious or non-conforming USB serial device that reports excessive transmit credits. No local account on the victim is required for the device-side attacker, but the attack is not network reachable. Realistic exploitation normally requires physical access, supply-chain compromise, a malicious peripheral, or a user attaching the device.

Namespaces and containers do not materially reduce the physical/device requirement. The vulnerable driver is not a broad default network-exposed path and depends on the io_edgeport USB serial driver being present and bound to compatible hardware. Call-site confidence is medium: the patch and commit describe the edge_interrupt_callback to edge_write consequence clearly, but detailed allocator adjacency and overwrite controllability are not shown.

## 4. Severity interpretation

This is not an ordinary Moderate resource bug because the patch describes a concrete OOB write in kernel memory. Realistic impact is most clearly local or physical DoS through kernel crash. Theoretical impact includes privilege escalation because kernel memory is overwritten, but the available patch context does not demonstrate arbitrary write, controlled target selection, object reuse, or a reliable LPE path.

Therefore the conservative handling is borderline/manual-review, while the paranoid handling is Actionable Moderate and should not be auto-closed.

## 5. One-sentence report phrase

A malicious or non-conforming USB Edgeport-compatible serial device can report excessive transmit credits, causing txCredits to exceed maxTxCredits and allowing edge_write to write beyond the allocated TX FIFO ring buffer, resulting in kernel memory corruption with at least DoS impact and possible privilege escalation.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the bug contains an explicit kernel OOB write primitive, even though practical exploitation is limited by physical or malicious-device reachability and the overwrite appears constrained.

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

Patch: USB: serial: io_edgeport: cap received transmit credits
Commit: ee57992c053a6d395e98ced2d4c9cc3b42d8c27a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee57992c053a6d395e98ced2d4c9cc3b42d8c27a

Commit description:

The interrupt-status packet reports transmit credits returned by the
device. edge_interrupt_callback() adds the 16-bit value to txCredits
without checking maxTxCredits.

edge_write() uses txCredits minus the software FIFO count as the amount
of data that fits. Since the FIFO is allocated with maxTxCredits bytes,
txCredits exceeding maxTxCredits can cause OOB write in ring buffer.

Cap accumulated credits at maxTxCredits. Conforming devices should never
hit the cap.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Assisted-by: Codex:GPT-5
Signed-off-by: Sunho Park <shpark061104@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/usb/serial/io_edgeport.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=ee57992c053a6d395e98ced2d4c9cc3b42d8c27a

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

The original Linux kernel CVE announcement for CVE-2026-68365 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68365

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:R/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.8

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: 4
  Paranoid ActionableScore: 6

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: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).