[CVE-2026-64175][LOW] wifi: iwlwifi: mld: stop TX during firmware restart

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

CVE: CVE-2026-64175
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: wifi: iwlwifi: mld: stop TX during firmware restart
Commit: dc31c69476520bb4c2a208211a8d3c310a62c4d0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dc31c69476520bb4c2a208211a8d3c310a62c4d0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64175
Analysis date: Sun, 19 Jul 2026 15:02:36 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
iwlwifi MLD could continue dequeuing and freeing TX skbs during firmware restart, causing CPU churn and memory pressure under sustained traffic, but the issue appears limited to local or workload-assisted denial of service without memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-64175 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64175

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-2026-64175	LOW	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:N/I:N/A:H';**CWE-400;CWE-703;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'iwlwifi mld TX can continue dequeuing frames while firmware restart is in progress after a firmware crash. Each dequeued skb is passed to the transport even though firmware is dead, so iwl_trans_tx returns EIO and the skb is immediately freed, creating CPU churn and slab allocation pressure under high throughput workloads. For the CVSS the PR:L is used because reliable triggering normally requires a local user or process workload that can generate sustained TX traffic while the device is in firmware restart. The issue is not directly network reachable as a packet parsing flaw, although remote traffic can contribute to the workload in deployments where the host sends traffic over the affected WiFi device. Impact is denial of service or degraded availability only, with no evidence of UAF, OOB access, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	REMOTE DANGER UAF NETWORK SKB KERNEL_PANIC_PLUS_UAF HARDWARE  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2

## 1. ActionableScore

* Conservative score: **2**
* Paranoid score: **2**
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Triggered signals:

* **Local unprivileged trigger: +1**
  A local unprivileged process can generate sustained TX traffic, for example UDP or SSH traffic, while the device is in firmware restart.

* **Firmware-mediated external influence: +1**
  The problematic state depends on an iwlwifi firmware crash and restart. External wireless conditions or traffic may contribute, but this is not a directly remote packet-parsing vulnerability.

* **Availability impact realistic: +1**
  The bug can cause CPU churn and skb allocation churn, leading to memory pressure and degraded availability under high-throughput restart scenarios.

Subtracted signals:

* **Hard or unreliable condition: -1**
  Reliable triggering requires a firmware crash or restart window plus sustained TX traffic. This is not a simple always-available local trigger.

Not awarded:

* **Remote reachable / network-triggerable: +0**
  Remote traffic may contribute to workload, but the bug is not directly triggered by parsing attacker-controlled network packets.

* **Generic memory corruption: +0**
  No UAF, double free, OOB write, heap overwrite, refcount misuse, or type confusion is shown.

* **Privilege escalation plausible: +0**
  The patch and described behavior only support resource pressure / DoS.

* **Reliable kernel crash / strong DoS: +0**
  The described effect is CPU and memory pressure from allocation churn, not a direct kernel panic or deterministic crash.

## 3. Reachability analysis

A local process can help trigger the condition by generating sustained outbound traffic while the affected iwlwifi device is in firmware restart. The firmware crash itself is a required precondition and may be hardware or firmware specific. Remote peers can contribute to traffic patterns, but they do not appear to have a direct protocol-level trigger for the kernel bug.

Namespaces and containers do not materially improve reachability unless the container can drive traffic through the affected WiFi interface. No CAP_SYS_ADMIN or CAP_NET_ADMIN appears necessary merely to generate traffic, but reliable reproduction depends on the firmware restart state.

The path is limited to the iwlwifi MLD sub-driver and affected Intel WiFi 7 style deployments, so it is not a broad core networking exposure.

## 4. Severity interpretation

This behaves like an **ordinary Moderate / Low-like resource pressure issue**, not an Important-class vulnerability. The realistic impact is degraded availability from CPU churn and skb allocation pressure during firmware restart. There is no evidence of memory corruption, privilege escalation, confidentiality impact, or integrity impact.

The theoretical worst case remains DoS/resource exhaustion. It should not be elevated to Actionable Moderate or Important based on the provided patch.

## 5. One-sentence report phrase

iwlwifi MLD could continue dequeuing and freeing TX skbs during firmware restart, causing CPU churn and memory pressure under sustained traffic, but the issue appears limited to local or workload-assisted denial of service without memory corruption or privilege escalation.

## 6. Manual review recommendation

**NO MANUAL CHECK NEEDED**

This is a resource pressure / DoS-only issue with no demonstrated memory corruption primitive, no security-boundary bypass, and no direct remote trigger.

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

Patch: wifi: iwlwifi: mld: stop TX during firmware restart
Commit: dc31c69476520bb4c2a208211a8d3c310a62c4d0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dc31c69476520bb4c2a208211a8d3c310a62c4d0

Commit description:

When iwlwifi firmware crashes (e.g., NMI_INTERRUPT_UNKNOWN on Intel
BE201/Wi-Fi 7), iwl_mld_nic_error() sets mld->fw_status.in_hw_restart
to true. However, iwl_mld_tx_from_txq() does not check this flag before
dequeuing frames from mac80211 and pushing them to the transport layer.

Since the firmware is dead, iwl_trans_tx() returns -EIO for each frame,
which then gets freed immediately. Under high-throughput conditions
(e.g., Tailscale UDP traffic or active SSH sessions), this creates a
tight dequeue-send-fail-free loop that wastes CPU cycles and generates
rapid skb allocation churn, leading to memory pressure from slab
fragmentation.

The RX path already has this guard (iwl_mld_rx_mpdu checks
in_hw_restart at rx.c:1906), and so does the TXQ allocation worker
(iwl_mld_add_txqs_wk at tx.c:156). Add the same guard to
iwl_mld_tx_from_txq() to stop all TX during firmware restart.

Frames left in mac80211's TXQs are naturally drained after restart
completes, when queue reallocation triggers iwl_mld_tx_from_txq()
via iwl_mld_add_txq_list(), or when new upper-layer traffic invokes
wake_tx_queue.

Tested on ASUS Zenbook 14 UX3405CA with Intel BE201 (Wi-Fi 7) on
kernel 6.19.5 where the firmware crashes approximately every 10-15
minutes under Tailscale traffic.

Fixes: d1e879e ("wifi: iwlwifi: add iwlmld sub-driver")
Cc: stable@vger.kernel.org
Signed-off-by: Sheroz Juraev <goodmartiandev@gmail.com>
Link: https://patch.msgid.link/20260315081221.2678478-1-goodmartiandev@gmail.com
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/wireless/intel/iwlwifi/mld/tx.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=dc31c69476520bb4c2a208211a8d3c310a62c4d0

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

The original Linux kernel CVE announcement for CVE-2026-64175 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64175

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:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: unknown
  Paranoid ActionableScore: 2

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).