[CVE-2026-64574][MODERATE 7.0] wifi: mac80211: tear down new links on vif update error path [ Upstream

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

CVE: CVE-2026-64574
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: wifi: mac80211: tear down new links on vif update error path [ Upstream
Commit: 329589417214d3b7221432e5b266ed2bba7ff674
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=329589417214d3b7221432e5b266ed2bba7ff674
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64574
Analysis date: Wed, 05 Aug 2026 04:52:10 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A mac80211 VIF link update error path can free newly added MLO link containers while leaving per-link debugfs files with dangling private_data, allowing a later local debugfs read to trigger a use-after-free and kernel crash.

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

The original Linux kernel CVE announcement for CVE-2026-64574 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64574

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
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CVE-2026-64574	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:L/I:L/A:H';*CWE-416;*CWE-672;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'mac80211 can leave per link debugfs files with file private_data pointing to freed link containers when ieee80211_vif_update_links adds links and drv_change_vif_links later fails. A later open and read of a surviving debugfs file such as link-1/txpower can dereference freed memory in ieee80211_if_read_link and crash the kernel. For the CVSS the PR:L is used in the paranoid score because limited local privileges may be enough in deployments where debugfs access or wireless administration is delegated, although typical systems restrict this path to administrators. The issue is local and is not network reachable through packet traffic. Impact is at least denial of service via kernel crash and in worst case may allow limited confidentiality or integrity impact due to a dangling pointer UAF, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	REMOTE READ OOB DANGER ERRORPATH UAF DEBUGFS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	guess

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Generic memory corruption: +2. The bug is a real use-after-free through a stale debugfs file private_data pointer.
* Real lifetime corruption: +1. Newly allocated link containers can be freed while debugfs entries still reference them.
* Reliable kernel crash / strong DoS: +1. The report includes KASAN slab-use-after-free followed by general protection fault and kernel panic.
* Requires admin/root/CAP_NET_ADMIN/debugfs access in typical deployments: -2. Creating the failed MLO link update state and reading mac80211 debugfs files is normally restricted.
* Rare or configuration-dependent path: -1. This depends on mac80211 MLO link handling, debugfs exposure, and a drv_change_vif_links failure path.

Paranoid additions/interpretation:

* Local limited-privilege trigger: +1. In some deployments, wireless administration or debugfs access may be delegated to a reduced-privilege service, container root, or local operator account rather than full host root.
* Confidentiality/integrity concern is limited. The stale pointer UAF is read through debugfs, but the patch does not show attacker-controlled reclaim, overwrite, callback dispatch, or type confusion. Therefore this is not scored as strong LPE.
* Paranoid score is kept at 5 because this is a real lifetime UAF with a demonstrated crash, but without a demonstrated reclaim or write primitive.

## 3. Reachability analysis

The bug is local. It is not network reachable through WiFi packet traffic. Triggering requires a VIF link update that adds new MLO links, followed by failure of drv_change_vif_links, then later open/read of the surviving per-link debugfs file.

Typical systems require administrative privileges for the control path and for debugfs access, so the conservative interpretation treats this as privileged local DoS. Namespaces or containers can matter if CAP_NET_ADMIN, debugfs, or wireless control is delegated to a less trusted context. Firmware or driver failure can help make the error path reachable, but it is not enough to classify the issue as remotely triggerable.

Call-site confidence: high. The commit message describes the allocation, debugfs registration, failed rollback path, dangling file private_data, and later read path into ieee80211_if_read_link.

## 4. Severity interpretation

This is stronger than an ordinary Moderate cleanup bug because it is a confirmed UAF with a surviving externally accessible debugfs object and a demonstrated kernel panic. Realistic exploitation evidence supports local DoS. Privilege escalation is not strongly demonstrated because there is no shown attacker-controlled reclaim, object replacement, write-after-free, callback control, or refcount takeover.

Conservative handling is borderline manual review. Paranoid handling is Actionable Moderate because lifetime UAFs in kernel objects are historically under-triaged when only the crash path is shown.

## 5. One-sentence report phrase

A mac80211 VIF link update error path can free newly added MLO link containers while leaving per-link debugfs files with dangling private_data, allowing a later local debugfs read to trigger a use-after-free and kernel crash.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: confirmed UAF with dangling debugfs private_data and demonstrated kernel panic. No strong LPE primitive is shown, but the lifetime bug class and possible delegated local access make auto-close unsafe.

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

Patch: wifi: mac80211: tear down new links on vif update error path [ Upstream
Commit: 329589417214d3b7221432e5b266ed2bba7ff674
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=329589417214d3b7221432e5b266ed2bba7ff674

Changed files:
  net/mac80211/debugfs_netdev.c
  fs/debugfs/file.c
  fs/read_write.c
  arch/x86/entry/syscall_64.c
  arch/x86/entry/entry_64.S
  net/mac80211/link.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=329589417214d3b7221432e5b266ed2bba7ff674

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

The original Linux kernel CVE announcement for CVE-2026-64574 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64574

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: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: 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: NO
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).