[CVE-2026-74263][LOW] net: wwan: t7xx: check skb_clone in control TX [ Upstream

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

CVE: CVE-2026-74263
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net: wwan: t7xx: check skb_clone in control TX [ Upstream
Commit: 7edd4db82f9429591de10be4c904c817f12ba029
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7edd4db82f9429591de10be4c904c817f12ba029
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74263
Analysis date: Sun, 16 Aug 2026 05:12:10 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like. Auto-close candidate
Manual review required: NO

Summary:
A NULL pointer dereference in the t7xx WWAN control TX path can occur when `skb_clone()` fails and the returned pointer is used immediately, allowing a local user or service with access to the WWAN interface to cause a kernel crash under memory pressure.

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

The original Linux kernel CVE announcement for CVE-2026-74263 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74263

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-74263	LOW	CHECK WITH IMPACT FROM ORIG NN NONE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-690;**CWE-476;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 't7xx_port_ctrl_tx() clones each skb fragment with skb_clone() and then immediately writes to cloned len. If skb_clone() fails under memory pressure, cloned is NULL and the driver can dereference a NULL pointer in the kernel. For the CVSS the PR:L is used for the paranoid score because triggering requires a local user or local service with access to the WWAN control TX interface rather than remote packet delivery. The issue is not directly network reachable. Impact is denial of service via kernel crash or oops. No concrete UAF, OOB write, information leak, or privilege escalation primitive is visible from the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. Auto-close candidate (with actual score 1)  SKIP CVE-2026-74263 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	NULLPTR NOMEMCHK SIMPLEFIX NETWORK SKB LINUS  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like. Auto-close candidate**::

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. `skb_clone()` can return NULL and the old code immediately dereferenced `cloned->len`, causing a NULL pointer dereference.
* Hard or unreliable condition required: -1. The failure requires allocation failure or memory pressure at the relevant TX path.
* Rare AND difficult-to-reach subsystem/configuration: -1. This is specific to the MediaTek t7xx WWAN driver and requires the relevant hardware or driver path.
* Score floor applied: 0.

Paranoid adjustment:

* Local unprivileged trigger: +1. If a local user or local service has access to the WWAN control TX interface, it may be able to drive the vulnerable path.
* Resulting paranoid score: 1.

Not awarded:

* No generic memory corruption. This is a NULL pointer dereference, not UAF, double free, OOB write, or type confusion.
* No LPE plausibility. The patch does not show attacker-controlled reclaim, overwrite, stale callback, object confusion, or refcount abuse.
* No confidentiality or integrity impact. The visible primitive is crash-only.
* No remote/network-triggerable signal. This is not triggered by remote packet delivery.

Call-site confidence: high. The patch shows the immediate failing use of `cloned` after `skb_clone()`.

## 3. Reachability analysis

The bug is reachable through the t7xx WWAN control TX path, not through normal remote network traffic. A realistic trigger requires a system with the t7xx driver active, access to the relevant WWAN interface or device path, and conditions where `skb_clone(..., GFP_KERNEL)` fails. Namespaces or containers may matter only if the device node or WWAN control interface is delegated into the container. In typical deployments this is hardware-specific and not broadly exposed.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like local DoS. The theoretical impact is a kernel crash or oops from NULL dereference. There is no evidence of memory corruption beyond invalid NULL dereference, no practical privilege escalation path, and no cross-boundary data access. The CVSS-style paranoid DoS score can be moderate, but the practical actionable score remains low.

## 5. One-sentence report phrase

A NULL pointer dereference in the t7xx WWAN control TX path can occur when `skb_clone()` fails and the returned pointer is used immediately, allowing a local user or service with access to the WWAN interface to cause a kernel crash under memory pressure.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: crash-only NULL dereference, hardware-specific WWAN path, no remote reachability, and no visible UAF/OOB/write or privilege escalation primitive.

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

Patch: net: wwan: t7xx: check skb_clone in control TX [ Upstream
Commit: 7edd4db82f9429591de10be4c904c817f12ba029
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7edd4db82f9429591de10be4c904c817f12ba029

Changed files:
  drivers/net/wwan/t7xx/t7xx_port_wwan.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=7edd4db82f9429591de10be4c904c817f12ba029

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

The original Linux kernel CVE announcement for CVE-2026-74263 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74263

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:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 0
  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).