[CVE-2026-80947][MODERATE 7.0] wifi: rtl8xxxu: fix use-after-free from rx_urb_wq on stop

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

CVE: CVE-2026-80947
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: rtl8xxxu: fix use-after-free from rx_urb_wq on stop
Commit: 800d2b490a9af1e7132a3564c2ad5a81292e5b40
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=800d2b490a9af1e7132a3564c2ad5a81292e5b40
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80947
Analysis date: Fri, 11 Sep 2026 16:41:48 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80947 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80947

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-80947	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80947 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A use after free can occur in the rtl8xxxu WiFi driver because rx_urb_wq may remain queued or running while the device stop and disconnect path tears down RX URBs and later frees priv. Active RX traffic can arm the worker from the RX completion path, and a following stop or USB disconnect can let rtl8xxxu_rx_urb_work recover a stale priv pointer and dereference priv udev after ieee80211_free_hw. For the CVSS the PR:L is selected for the paranoid score because reliable triggering usually requires a local user context or delegated device control to cause the stop or disconnect condition, while nearby wireless traffic alone is not enough to complete the teardown race. The issue is not directly network reachable. Adjacent wireless traffic may help create RX pressure, but the security boundary crossing depends on a local teardown event. Impact is at least denial of service via kernel crash, and in worst case may allow broader confidentiality or integrity impact due to a real use after free race in kernel memory.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)	YES	REMOTE INIT RACE ERRORPATH UAF NETWORK SKB LINUS KPANIC  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 4
* Paranoid score: 4
* Final recommended bucket: **Borderline / manual review recommended**::

No floor or cap was applied. REAL UAF FLOOR 5 was not applied because this is a teardown style async workqueue UAF with fixed driver context, no demonstrated controlled reclaim, no concrete repeated release/refcount mutation, and no independently useful post-free exploitation primitive.

2. Signal breakdown

Conservative positive signals:

* +2 Real UAF / active lifetime violation. `rx_urb_wq` can run after `rtl8xxxu_disconnect()` and `ieee80211_free_hw()` free `priv`, and the worker recovers `priv` via `container_of`.
* +1 Reliable kernel crash / strong DoS. The stale worker dereferences `priv->udev` and may resubmit URBs after teardown, supporting a kernel fault or crash.

Conservative negative signals:

* 0 No host-admin penalty applied. Host-admin-equivalent privilege is not positively established from the supplied evidence.
* 0 No race penalty applied in the conservative arithmetic. Although this is a teardown race, the evidence also shows an active RX workload can arm the worker before stop/disconnect.

Paranoid additional signal:

* +1 Attacker-influenced async lifetime condition. Active RX traffic can help arm `rx_urb_wq`, and a following stop or disconnect can expose the stale worker window. This is enough for a higher review score, but not enough for strong exploitation leverage.

Important non-awarded signals:

* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Callback or function pointer control not demonstrated.
* Concrete repeated release/refcount mutation not demonstrated.
* Structured stale-object leverage not awarded because the stale use is mainly fixed driver-context teardown processing.
* Weak LPE not awarded merely because this is a UAF.
* Extra Availability not awarded because the same crash is already counted once.
* C/I impact not awarded in ActionableScore because no disclosure, directed corruption, or privilege-escalation primitive is established.
* Remote reachability not awarded. Wireless RX traffic may help create pressure, but the complete trigger also needs stop/disconnect teardown.

Repeated release/refcount checklist:

* First release can end lifetime: yes, `ieee80211_free_hw()` frees `priv`.
* Exact same reference survives: the queued work item embedded in `priv` can still recover the stale `priv`.
* Second operation is a real lifetime/refcount mutation: no concrete second put/free/refcount operation on the same object is shown.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 applied: no.

3. Reachability analysis

The complete trigger requires active RX traffic sufficient to arm `rx_urb_wq`, followed by device stop or USB disconnect. A nearby wireless actor may contribute RX pressure, but nearby traffic alone does not perform the stop/disconnect step. A local user with delegated network or device-control capability may be able to trigger stop, while physical unplug may also cause disconnect, but the supplied evidence does not prove an ordinary unprivileged local software-only trigger.

HostAdminRequired is UNKNOWN because the complete privilege boundary for reliable stop/disconnect triggering is not fully established. NamespaceScopedPrivilege is NO because this is a physical USB WiFi driver teardown path, not a demonstrated namespace-scoped operation. No prior special kernel configuration is indicated beyond having affected rtl8xxxu hardware and the driver in use. The race is a teardown race, but active RX traffic can make the arming condition more plausible.

4. Primitive and severity interpretation

The exact primitive is a real use-after-free of the rtl8xxxu private driver state. The stale object is a fixed driver context used by an asynchronous workqueue after device teardown. The stale path dereferences structured fields such as `priv->udev` and can submit URBs after `usb_kill_anchored_urbs()` returned, but the supplied evidence does not show controlled reclaim, attacker-shaped replacement contents, arbitrary read/write, or callback control.

This is PrimitiveClass CLASS_B because a real kernel lifetime violation exists. It is not CLASS_A because no strong exploitation primitive is established. It is not CLASS_C because the issue is more than a plain NULL dereference or warning: the worker can run after the owning object is freed.

The demonstrated consequence is kernel crash or denial of service. The speculative consequence is broader memory-corruption impact if reclaim/reuse were later proven, but that is not established by the patch. ImportantCandidate is NO because the known mechanics look like a constrained async teardown UAF rather than an Important-preserving primitive. AutoDowngradeAllowed is YES because the unresolved evidence does not currently show meaningful exploitation leverage beyond crash, and there is no repeated lifetime/refcount mutation.

Likely operational severity: borderline Moderate with manual review recommended due to real UAF, but not a strong Important candidate from the supplied evidence alone.

5. One-sentence report phrase

A real use-after-free in the rtl8xxxu WiFi driver can let rx_urb_wq run after device teardown and dereference freed driver private state, causing a likely local or physical-triggered kernel crash without a demonstrated privilege-escalation primitive.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is a real kernel UAF in asynchronous driver teardown, but the supplied patch supports crash/DoS more strongly than controlled corruption or LPE.

7. Call-site confidence

Call-site confidence: high

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

Patch: wifi: rtl8xxxu: fix use-after-free from rx_urb_wq on stop
Commit: 800d2b490a9af1e7132a3564c2ad5a81292e5b40
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=800d2b490a9af1e7132a3564c2ad5a81292e5b40

Commit description:

rtl8xxxu arms rx_urb_wq from the RX completion path:
rtl8xxxu_rx_complete() hands the URB to rtl8xxxu_queue_rx_urb(), which
queues it on rx_urb_pending_list and, once the list grows past
RTL8XXXU_RX_URB_PENDING_WATER, schedules rx_urb_wq.  The worker
rtl8xxxu_rx_urb_work() drains rx_urb_pending_list, recovers priv through
container_of, and resubmits each URB through rtl8xxxu_submit_rx_urb(),
which anchors it on rx_anchor and dereferences priv->udev.

rtl8xxxu_stop() cancels the sibling work items (c2hcmd_work, ra_watchdog,
update_beacon_work) but never cancels rx_urb_wq, so a worker armed during
the last burst of RX traffic can run rtl8xxxu_rx_urb_work() after
rtl8xxxu_disconnect() has called ieee80211_free_hw(), which frees priv,
producing a use-after-free.  The window opens under active RX traffic
(pending count above the watermark) followed by a disconnect.

There are two teardown races to close:

  * rtl8xxxu_queue_rx_urb() decided whether to enqueue under rx_urb_lock
    but called schedule_work() after dropping the lock.  A completion
    that observed shutdown == false and released the lock could then call
    schedule_work() after rtl8xxxu_stop() had set shutdown and
    cancel_work_sync() had already returned, arming the worker to run
    after the teardown.  Move schedule_work() under the same !shutdown
    branch so the arming decision is atomic with the shutdown check.

  * rtl8xxxu_rx_urb_work() anchors every URB it drained back onto
    rx_anchor through rtl8xxxu_submit_rx_urb().  A worker still running
    when usb_kill_anchored_urbs(&priv->rx_anchor) returned would submit a
    URB that escaped the kill.  In rtl8xxxu_stop(), call
    cancel_work_sync(&priv->rx_urb_wq) before the kill so the worker is
    drained first.

After priv->shutdown is set under rx_urb_lock, completions can no longer
queue rx_urb_wq. cancel_work_sync() then drains the last queued or running
worker, and the following usb_kill_anchored_urbs() kills the URBs it may
have submitted.

rtl8xxxu_disconnect() is covered because ieee80211_unregister_hw()
guarantees .stop() runs for a live interface before ieee80211_free_hw()
frees priv.  The probe error path needs no cancel: rx_urb_wq is
INIT_WORK()'d there but cannot have been scheduled, since no URB is
submitted before ieee80211_register_hw() succeeds.

This bug was found by static analysis.

Fixes: 26f1fad ("New driver: rtl8xxxu (mac80211)")
Cc: stable@vger.kernel.org
Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20260630033117.3377-1-fanwu01@zju.edu.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/wireless/realtek/rtl8xxxu/core.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=800d2b490a9af1e7132a3564c2ad5a81292e5b40

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

The original Linux kernel CVE announcement for CVE-2026-80947 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80947

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

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: 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).