[CVE-2026-72004][LOW] wifi: mac80211: fix memory leak in ieee80211_register_hw()

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

CVE: CVE-2026-72004
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: wifi: mac80211: fix memory leak in ieee80211_register_hw()
Commit: f01eec75fd372961550b928902f3a2c11fca1daf
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f01eec75fd372961550b928902f3a2c11fca1daf
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72004
Analysis date: Sat, 15 Aug 2026 20:51:01 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A memory leak in mac80211 ieee80211_register_hw() can occur when kmemdup() fails during supported band copying, causing the error path to skip rate_control_deinitialize() and leak local rate_ctrl state, but exploitation normally requires privileged driver registration control and only supports resource exhaustion DoS.

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

The original Linux kernel CVE announcement for CVE-2026-72004 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72004

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.

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

CVE-2026-72004	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;CWE-404;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.1';DESCR 'A memory leak in mac80211 can occur in ieee80211_register_hw() when kmemdup() fails while copying supported band data. The failure path skipped rate_control_deinitialize() after rate control had already been initialized, leaving the local rate_ctrl object referenced only by leaked cleanup state. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over driver probe or module load and a kmemdup() failure during device registration. The issue is not network reachable because it is in the device registration error path rather than WiFi frame processing. Impact is resource leakage and possible denial of service only under repeated failed registration or severe memory pressure.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	REMOTE SIMPLEFIX LEAK ERRORPATH HARDWARE TEST 	YES	NO	checked

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

ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

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

## 2. Signal breakdown

Triggered signals:

* Availability impact realistic: +1, paranoid only. Repeated failed device registration under memory pressure could leak rate control state and eventually contribute to resource exhaustion.
* Requires admin/root/CAP_* in typical deployments: -2. Reliable triggering normally requires driver probe/module/device registration control.
* Hard or unreliable trigger condition: -1. The leak requires kmemdup() failure at a specific point in ieee80211_register_hw(), i.e. ENOMEM during supported band duplication.
* Broad/common subsystem: +1, weakly applicable. mac80211 is common, but this exact path is device registration/error handling, not normal WiFi packet processing.

Not triggered:

* No remote reachability.
* No local unprivileged trigger shown.
* No UAF, double free, OOB write, type confusion, refcount takeover, or arbitrary write.
* No plausible privilege escalation primitive.
* No confidentiality or integrity impact.

## 3. Reachability analysis

The affected code is in ieee80211_register_hw(), during mac80211 hardware registration. The vulnerable path is reached only if kmemdup() fails while copying supported band structures after rate control has already been initialized. In normal deployments, unprivileged users cannot directly register mac80211 hardware or reliably force this exact allocation failure. Namespaces or containers do not normally reduce this to an unprivileged trigger unless the environment delegates device or module management in an unusual way. The path is not network reachable and is unrelated to WiFi frame receive/transmit parsing.

Call-site confidence: high. The patch shows the exact failure path and the cleanup labels, and the consequence is a skipped rate_control_deinitialize() call.

## 4. Severity interpretation

This behaves like a low severity resource leak rather than an actionable Moderate or Important kernel vulnerability. The theoretical impact is memory/resource exhaustion after repeated failed registration attempts, but the patch does not indicate memory corruption, stale pointer reuse, attacker-controlled reclaim, or privilege escalation. Realistic exploitation requires privileged device-management control plus a hard-to-hit ENOMEM condition.

## 5. One-sentence report phrase

A memory leak in mac80211 ieee80211_register_hw() can occur when kmemdup() fails during supported band copying, causing the error path to skip rate_control_deinitialize() and leak local rate_ctrl state, but exploitation normally requires privileged driver registration control and only supports resource exhaustion DoS.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a cleanup-path memory leak with no concrete corruption or privilege boundary bypass primitive, and it can be handled as a low-priority/autoclose candidate unless the evaluated product exposes untrusted driver probe or module load control.

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

Patch: wifi: mac80211: fix memory leak in ieee80211_register_hw()
Commit: f01eec75fd372961550b928902f3a2c11fca1daf
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f01eec75fd372961550b928902f3a2c11fca1daf

Commit description:

If kmemdup() fails while copying supported band structures, the error
path jumps to fail_rate. This skips rate_control_deinitialize() and
leaks the initialized local->rate_ctrl.

Fix this by adding a fail_band label that shares the rate-control cleanup
path before falling through to the remaining teardown.

The bug was first flagged by an experimental analysis tool we are
developing for kernel memory-management bugs while analyzing
v6.13-rc1. The tool is still under development and is not yet publicly
available. Manual inspection confirms that the bug is still present in
v7.1-rc7.

An x86_64 allyesconfig build showed no new warnings. As we do not have a
suitable mac80211 device/driver combination to test with, no runtime
testing was able to be performed.

Fixes: 09b4a4f ("mac80211: introduce capability flags for VHT EXT NSS support")
Cc: stable@vger.kernel.org
Reviewed-by: Zilin Guan <zilin@seu.edu.cn>
Signed-off-by: Dawei Feng <dawei.feng@seu.edu.cn>
Link: https://patch.msgid.link/20260706143507.146131-1-dawei.feng@seu.edu.cn
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/mac80211/main.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=f01eec75fd372961550b928902f3a2c11fca1daf

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

The original Linux kernel CVE announcement for CVE-2026-72004 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72004

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:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.1

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).