[CVE-2026-64117][MODERATE 7.0] wifi: mac80211: capture fast-RX rate before mesh reuses skb->cb

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

CVE: CVE-2026-64117
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: mac80211: capture fast-RX rate before mesh reuses skb->cb
Commit: 2fb64f94f9afb774f2fa0c7835727d7a67f89f07
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2fb64f94f9afb774f2fa0c7835727d7a67f89f07
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64117
Analysis date: Sun, 19 Jul 2026 15:41:02 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A use-after-free read in the mac80211 mesh fast-RX path can be triggered by adjacent 802.11 mesh traffic when RX status stored in `skb->cb` is used after the skb control buffer is reused or freed, causing a potential kernel crash and requiring manual review due to the network-facing lifetime bug.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64117 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64117

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-2026-64117	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-825;*CWE-664;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'A use-after-free read in the mac80211 mesh fast RX path can occur because ieee80211_invoke_fast_rx keeps using RX status stored in skb cb after ieee80211_rx_mesh_data may reuse the same control buffer as TX info or free the skb in the no-route path. An adjacent attacker able to inject or influence 802.11 mesh traffic may trigger the path by causing unicast mesh forwarding that returns RX_QUEUED, after which the caller encodes the rate from stale or freed memory. For the CVSS the PR:N is used for the paranoid score because no local user account on the victim is required when the vulnerable mesh RX path is reachable over the wireless link, although practical triggering depends on mesh configuration and proximity. The issue is not Internet reachable and is limited to adjacent Wi-Fi or local mesh network range. Impact is at least denial of service through a kernel use-after-free condition and KASAN reported slab-use-after-free. Worst case may allow limited confidentiality or integrity impact if freed skb control buffer contents are reused in a sensitive way, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE UAF SKB KPANIC  KPANIC LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS 	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2
  The trigger is adjacent-network reachable through 802.11 mesh traffic. It is not Internet-reachable, but it can be driven over the wireless link when mesh fast-RX forwarding is active.

* Memory corruption, weak/indirect corruption candidate: +1
  The bug is a use-after-free read from `skb->cb` through stale RX status. The patch does not show attacker-controlled reclaim, overwrite, callback control, type confusion, or arbitrary write.

* Real lifetime corruption: +1
  `ieee80211_rx_mesh_data()` can free the skb before the caller uses `status`, leaving a stale pointer into freed skb storage.

* Reliable kernel crash / strong DoS: +1
  The commit explicitly reports KASAN slab-use-after-free in `ieee80211_prepare_and_rx_handle`. A kernel crash or panic is realistic, especially with hardening or debug configurations.

* Rare AND difficult-to-reach subsystem/configuration: -1
  The affected path requires mac80211 mesh fast-RX and a specific mesh unicast forwarding or no-route path. This is not a broad default Wi-Fi receive path.

Paranoid adjustment:

* Configuration penalty removed: +1 relative to conservative
  In deployments that actually use 802.11 mesh, the vulnerable path is directly exposed to adjacent wireless traffic. This makes the issue actionable even though the global deployment base is narrower.

Not counted:

* Privilege escalation plausible: +0
  No reclaim, overwrite, object replacement, callback dispatch, refcount takeover, or type confusion is shown.

* Confidentiality / integrity impact: +0 in score
  Limited C/I concern exists conceptually because freed control-buffer contents are read and encoded into stats, but the patch does not show a practical disclosure or modification primitive.

## 3. Reachability analysis

An attacker does not need a local account on the victim if they can inject or influence traffic in the affected 802.11 mesh environment. The realistic attacker is adjacent to the wireless mesh, not remote over the Internet. The vulnerable path depends on mesh fast-RX support and on `ieee80211_rx_mesh_data()` returning `RX_QUEUED` after either reusing `skb->cb` or freeing the skb. Namespaces and containers are not the main privilege boundary here because triggering is through wireless receive processing rather than a local syscall interface. Exposure is configuration-dependent, but on systems operating as mesh nodes it is a real network-facing kernel receive path.

Call-site confidence: high. The commit message and diff show the relevant call order, the stale `status` use, the freeing/reuse condition, and the exact fix.

## 4. Severity interpretation

This behaves above an ordinary Moderate because it is an adjacent-network-triggerable lifetime bug in a kernel packet receive path. It does not reach Strong Important based on the provided evidence because the observed primitive is a stale read from freed skb control-buffer storage, not a demonstrated write-after-free, object replacement, type confusion, or privilege-escalation path. The conservative view is borderline manual-review territory. The paranoid view is Actionable Moderate because wireless-adjacent triggering plus UAF-class behavior should not be auto-closed without review.

## 5. One-sentence report phrase

A use-after-free read in the mac80211 mesh fast-RX path can be triggered by adjacent 802.11 mesh traffic when RX status stored in `skb->cb` is used after the skb control buffer is reused or freed, causing a potential kernel crash and requiring manual review due to the network-facing lifetime bug.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is a UAF-class issue in an adjacent-network receive path with an explicit KASAN slab-use-after-free report. Even though the currently visible primitive looks closer to DoS than LPE, the combination of network reachability, skb lifetime corruption, and mesh forwarding semantics should be reviewed manually.

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UPSTREAM PATCH SUMMARY
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Patch: wifi: mac80211: capture fast-RX rate before mesh reuses skb->cb
Commit: 2fb64f94f9afb774f2fa0c7835727d7a67f89f07
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2fb64f94f9afb774f2fa0c7835727d7a67f89f07

Commit description:

ieee80211_invoke_fast_rx() reads RX status through
IEEE80211_SKB_RXCB(skb), which aliases the same skb->cb storage
that ieee80211_rx_mesh_data() reuses as IEEE80211_TX_INFO.  In the
unicast forward path, mesh_data does:

	info = IEEE80211_SKB_CB(fwd_skb);
	memset(info, 0, sizeof(*info));

on the same skb the caller still names via rx->skb, then either
queues the skb for TX (success) or kfree_skb()'s it (no-route)
before returning RX_QUEUED.  The caller's RX_QUEUED arm then
calls sta_stats_encode_rate(status) on memory that is either
zeroed (success path) or freed (no-route path).  The latter is
KASAN slab-use-after-free in ieee80211_prepare_and_rx_handle.

Fix by encoding the rate from status before invoking
ieee80211_rx_mesh_data(), so the RX_QUEUED arm consumes a value
captured while status was still backed by valid memory.

Fixes: 3468e1e ("wifi: mac80211: add mesh fast-rx support")
Cc: stable@vger.kernel.org
Signed-off-by: Zhao Li <enderaoelyther@gmail.com>
Link: https://patch.msgid.link/20260509043427.60322-2-enderaoelyther@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/mac80211/rx.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=2fb64f94f9afb774f2fa0c7835727d7a67f89f07

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

The original Linux kernel CVE announcement for CVE-2026-64117 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64117

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:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.4

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).