[CVE-2026-52982][MODERATE REGULAR] net: usb: rtl8150: fix use-after-free in rtl8150_start_xmit() [ Upstream

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

CVE: CVE-2026-52982
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: usb: rtl8150: fix use-after-free in rtl8150_start_xmit() [ Upstream
Commit: 5af290c86fa81ddbc86a08d54229af5daa40c6a4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5af290c86fa81ddbc86a08d54229af5daa40c6a4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52982
Analysis date: Wed, 24 Jun 2026 13:02:19 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A race in the rtl8150 USB Ethernet transmit path can free an SKB in the URB completion handler before `rtl8150_start_xmit()` reads `skb->len` for statistics, causing a local UAF read with likely DoS impact and no demonstrated privilege-escalation primitive.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-52982 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52982

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-2026-52982	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A race based use-after-free read in the rtl8150 USB Ethernet transmit path occurs because rtl8150_start_xmit() reads skb len for TX statistics after usb_submit_urb() has been called. The USB URB completion handler can run on another CPU before the submitter updates stats and can free the skb, so the later skb len access becomes a UAF read. For the CVSS the PR:L value is used because a local unprivileged user or process that can generate outbound traffic through the affected interface may be able to reach the transmit path, while direct network only triggering is not reliable. The issue is not directly network reachable from a remote peer in the normal sense because it is in the local TX path for a USB NIC. Impact is at least local denial of service via kernel crash or KASAN panic. For the paranoid score, limited confidentiality or integrity impact is kept possible because a freed skb field is read after reuse, but there is no supported arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4)	YES	READ DANGER USB UAF NETWORK SKB HARDWARE LINUS SYZBOT PACKET  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

* Local unprivileged trigger: +1
  A local user or process that can generate outbound traffic through the affected rtl8150 interface can reach `rtl8150_start_xmit()`.

* Memory corruption, weak primitive: +1
  This is a real UAF read, but the stale access is a 4 byte read of `skb->len` for statistics. The patch does not show attacker-controlled reclaim, write-after-free, callback dispatch, type confusion, or arbitrary write.

* Real lifetime corruption: +1
  The SKB can be freed by the USB URB completion path before the transmit submitter finishes using it.

* Reliable kernel crash / strong DoS concern: +1
  KASAN reports a slab-use-after-free. On hardened or debug kernels this can be a crash or panic. On production kernels the observed primitive is weaker, but availability impact is still plausible.

* Hard or timing-dependent race: -1 in conservative score
  The bug depends on URB completion racing with the submitter. The paranoid score does not subtract this because syzbot demonstrated the race and USB completion on another CPU is a realistic asynchronous path.

Signals not awarded:

* Remote reachable: +0
  This is the local TX path of a USB NIC. A remote peer may indirectly cause responses, but reliable triggering by network input alone is not established.

* Privilege escalation plausible: +0
  No reclaim control, stale object replacement, write primitive, callback influence, or refcount takeover is shown.

* Confidentiality / Integrity impact: +0
  The stale read is used for `tx_bytes` accounting. There is no clear disclosure channel or integrity corruption primitive beyond incorrect statistics.

## 3. Reachability analysis

The primary trigger is local traffic transmission through an affected `rtl8150` USB Ethernet device. No administrative privilege is normally required merely to send packets if the interface is already configured and usable by the local user. Containers or network namespaces may matter only if they are allowed to transmit through the affected physical interface or a passed-through netdev. The path is not a core networking receive path and is not directly Internet reachable. It also requires the specific rtl8150 driver and compatible USB hardware, so exposure is narrower than common TCP/IP or netfilter bugs.

## 4. Severity interpretation

This behaves like a borderline actionable Moderate rather than an Important-class issue. The bug is a genuine race-based UAF, so it should not be auto-dismissed as a harmless accounting bug. However, the demonstrated access is read-only, narrow, and used only for TX statistics after the SKB may already be freed. Realistic impact is mainly local DoS or KASAN/panic behavior. Theoretical memory-corruption concern exists because it is a lifetime bug, but the patch does not support a practical LPE path.

## 5. One-sentence report phrase

A race in the rtl8150 USB Ethernet transmit path can free an SKB in the URB completion handler before `rtl8150_start_xmit()` reads `skb->len` for statistics, causing a local UAF read with likely DoS impact and no demonstrated privilege-escalation primitive.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

This is a real UAF in a network driver and should receive manual review, but the primitive is weak and constrained enough that it does not look like a Strong Important candidate from the patch alone.

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

Patch: net: usb: rtl8150: fix use-after-free in rtl8150_start_xmit() [ Upstream
Commit: 5af290c86fa81ddbc86a08d54229af5daa40c6a4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5af290c86fa81ddbc86a08d54229af5daa40c6a4

Changed files:
  drivers/net/usb/rtl8150.c:712

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=5af290c86fa81ddbc86a08d54229af5daa40c6a4

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

The original Linux kernel CVE announcement for CVE-2026-52982 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52982

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:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 3
  Paranoid ActionableScore: 4

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).