[CVE-2026-64568][MODERATE 7.0] wifi: mac80211: fix unsol_bcast_probe_resp double free on alloc failure [ Upstream

[CVE-2026-64568][MODERATE 7.0] wifi: mac80211: fix unsol_bcast_probe_resp double free on alloc failure [ Upstream

[AL-KERNEL]

CVE: CVE-2026-64568
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: mac80211: fix unsol_bcast_probe_resp double free on alloc failure [ Upstream
Commit: ca27a81cd77b698e5eb586a011bee6800c7ee4bd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ca27a81cd77b698e5eb586a011bee6800c7ee4bd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64568
Analysis date: Wed, 05 Aug 2026 05:02:06 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A mac80211 AP configuration error can leave `unsol_bcast_probe_resp` pointing to an object already queued for `kfree_rcu()`, allowing a later update or teardown to trigger a kernel double free and crash, with possible but unproven privilege-escalation relevance.

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

The original Linux kernel CVE announcement for CVE-2026-64568 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64568

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.

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

CVE-2026-64568	MODERATE	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-415;*CWE-416;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A double free can occur in mac80211 unsol_bcast_probe_resp handling because ieee80211_set_unsol_bcast_probe_resp queued the old RCU object for freeing before the replacement allocation succeeded. If kzalloc fails, the stored pointer can still reference an object already queued for kfree_rcu, and a later update or AP teardown can queue the same rcu_head again. For the CVSS the PR:L is used because reliable triggering requires a local process with delegated wireless configuration capability such as CAP_NET_ADMIN rather than full system administration. The issue is not directly network reachable through Wi-Fi frames and is triggered through local control plane configuration. Impact is at least local denial of service via kernel crash and in the paranoid case may allow confidentiality or integrity impact because the primitive is kernel double free memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE OOB DANGER UAF KPANIC  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Triggered signals:

* Memory corruption, strong corruption primitive: +2
  The patch fixes a real double free of an RCU freed object in mac80211.
* Real lifetime corruption: +1
  The old `unsol_bcast_probe_resp` pointer can remain published while the object is already queued for `kfree_rcu()`.
* Reliable kernel crash / strong DoS: +1
  The commit includes a KASAN double-free report in `rcu_free_sheaf()`.
* Weak LPE concern: +1 paranoid only
  Kernel double free in `kmalloc-128` is a real corruption primitive, but no attacker-controlled reclaim or replacement primitive is shown.
* Broad/common subsystem exposure: +1
  mac80211 is a common Wi-Fi subsystem, though this specific AP configuration path is narrower.
* Hard condition / unreliable trigger: -1
  Reliable triggering requires an allocation failure after the old object was queued for RCU freeing.
* Requires CAP_NET_ADMIN-like control in typical deployments: -1 conservative
  Updating AP/mac80211 configuration is normally privileged, but delegated network administration can make this closer to PR:L than full host-root.

Call-site confidence: high. The relevant lifetime ordering and the freeing call are visible in the patch.

## 3. Reachability analysis

The bug is triggered through local wireless configuration control, not by ordinary remote Wi-Fi frames. A practical trigger needs the ability to update the unsolicited broadcast probe response template and then hit the allocation-failure path before a later update or AP teardown re-queues the same RCU object.

In typical deployments this requires a privileged process such as hostapd or a user with CAP_NET_ADMIN over the wireless interface. Namespaces or delegated network administration may reduce the practical privilege level, but this is not normally reachable by a fully unprivileged local user. The path is not Internet-reachable and is not a generic packet-processing receive path.

## 4. Severity interpretation

This is more than an ordinary Moderate correctness issue because the primitive is a real kernel double free with stale RCU lifetime state. Realistic exploitation evidence currently supports local DoS most strongly, because the demonstrated result is a KASAN double-free and the trigger depends on allocation failure.

Theoretical privilege escalation cannot be ruled out because double free is memory corruption, but the patch does not show controlled reclaim, type confusion, callback control, arbitrary write, or a stable replacement primitive. Therefore it is best treated as Actionable Moderate at minimum, with manual review needed before deciding whether it reaches Important severity.

## 5. One-sentence report phrase

A mac80211 AP configuration error can leave `unsol_bcast_probe_resp` pointing to an object already queued for `kfree_rcu()`, allowing a later update or teardown to trigger a kernel double free and crash, with possible but unproven privilege-escalation relevance.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a concrete kernel double-free and RCU lifetime bug. Even though realistic triggering appears local, privileged, and allocation-failure dependent, memory-corruption lifetime bugs of this class should not be auto-closed without human review.

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

Patch: wifi: mac80211: fix unsol_bcast_probe_resp double free on alloc failure [ Upstream
Commit: ca27a81cd77b698e5eb586a011bee6800c7ee4bd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ca27a81cd77b698e5eb586a011bee6800c7ee4bd

Changed files:
  mm/slub.c
  kernel/rcu/tree.c
  kernel/softirq.c
  net/mac80211/cfg.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=ca27a81cd77b698e5eb586a011bee6800c7ee4bd

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

The original Linux kernel CVE announcement for CVE-2026-64568 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64568

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: 4
  Paranoid ActionableScore: 5

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).