[CVE-2026-74488][IMPORTANT] wifi: mwifiex: use the subframe length when parsing A-MSDU TDLS frames

[CVE-2026-74488][IMPORTANT] wifi: mwifiex: use the subframe length when parsing A-MSDU TDLS frames

[AL-KERNEL]

CVE: CVE-2026-74488
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: wifi: mwifiex: use the subframe length when parsing A-MSDU TDLS frames
Commit: 25e5a3fe4f15e30f74eca42cbf3bcc3a3fbeda79
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=25e5a3fe4f15e30f74eca42cbf3bcc3a3fbeda79
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74488
Analysis date: Sat, 15 Aug 2026 15:43:19 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A mwifiex A-MSDU TDLS parsing bug uses the parent skb length for a subframe buffer, allowing an adjacent Wi-Fi attacker under TDLS and mwifiex conditions to trigger a UAF length read and possible OOB parsing, leading at least to kernel DoS and requiring manual review.

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

The original Linux kernel CVE announcement for CVE-2026-74488 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74488

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: IMPORTANT
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-2026-74488	IMPORTANT	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:H/I:H/A:H';*CWE-416;CWE-125;CWE-130;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '7.5';DESCR 'An A-MSDU TDLS parsing bug in mwifiex occurs because a subframe data pointer is passed to mwifiex_process_tdls_action_frame() with the parent skb length instead of the current subframe length. If the parent skb was already freed by ieee80211_amsdu_to_8023s(), reading the parent length is a use after free. If the parent skb is reused, the wrong length can overstate an earlier subframe and make TDLS IE parsing read or copy beyond the subframe boundary. The sender can influence A-MSDU subframe layout over Wi-Fi, but practical triggering requires mwifiex hardware, firmware TDLS support, and TDLS ethertype processing. For the CVSS the PR:N is used because no local account on the victim is required when a crafted adjacent wireless frame can reach the affected receiver. The issue is adjacent network reachable rather than Internet routable. Impact is at least denial of service via kernel crash, and the UAF or out of bounds read path makes limited confidentiality or integrity impact plausible enough for manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	REMOTE UAF NETWORK SKB KPANIC 	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 6
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Triggered signals:

* Remote reachable / network-triggerable: +2
  Crafted A-MSDU TDLS subframes can be supplied over Wi-Fi. This is adjacent-network reachable, not Internet-routable.

* Generic memory corruption: +2
  The patch context shows a real UAF read of `skb->len` after the parent skb may have been freed, plus an OOB read path when the parent length overstates the current subframe.

* Real lifetime corruption: +1
  The parent skb may be freed by `ieee80211_amsdu_to_8023s()` before `skb->len` is read.

* Reliable kernel crash / strong DoS: +1
  The parser can walk beyond the subframe boundary using an attacker-influenced length mismatch, making kernel crash realistic.

* Confidentiality impact plausible: +1
  OOB reads are plausible because TDLS IE parsing uses the wrong length-derived ceiling. No direct user-visible disclosure is proven, so this is a conservative memory-safety concern.

* Integrity impact plausible: +1 paranoid only
  The parser may consume copied out-of-bounds bytes as TDLS information elements, but no direct controlled write or state takeover is demonstrated.

Negative signals:

* Hard or unreliable triggering / special preconditions: -1
  Triggering requires mwifiex hardware, firmware TDLS support, TDLS ethertype handling, and suitable A-MSDU layout.

* Rare AND difficult-to-reach subsystem/configuration: -1
  mwifiex plus TDLS is narrower than common Wi-Fi or networking core receive paths.

Call-site confidence: high. The relevant caller and the incorrect `skb->len` versus `rx_skb->len` use are present in the supplied patch context.

## 3. Reachability analysis

An attacker does not need a local account on the victim. The realistic trigger is a crafted adjacent Wi-Fi frame or traffic path that reaches the affected mwifiex TDLS A-MSDU handling. This is not a generic Internet remote vulnerability because it depends on wireless adjacency, device support, firmware TDLS capability, and TDLS subframe processing.

Namespaces and containers do not materially reduce the trigger requirements because the input is received through the wireless data path rather than a local namespace-controlled API. The path is not broadly default-exposed on all systems, but affected systems with mwifiex hardware and TDLS enabled should treat this as externally influenced kernel memory-safety input.

## 4. Severity interpretation

This is more than an ordinary Moderate because it combines adjacent-network reachability with UAF and OOB-read indicators in a kernel packet-processing path. The conservative interpretation is Actionable Moderate because practical exploitation has meaningful hardware and protocol preconditions and no arbitrary write or privilege-escalation primitive is shown.

The paranoid interpretation reaches score 6 because the bug involves memory lifetime corruption and attacker-controlled frame layout. It should not be auto-closed. It is not enough to claim likely code execution, but it is enough to require manual review.

## 5. One-sentence report phrase

A mwifiex A-MSDU TDLS parsing bug uses the parent skb length for a subframe buffer, allowing an adjacent Wi-Fi attacker under TDLS and mwifiex conditions to trigger a UAF length read and possible OOB parsing, leading at least to kernel DoS and requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: adjacent-network reachable memory safety with UAF and OOB-read behavior. No proven arbitrary write or LPE primitive is shown, but the bug class and packet-controlled layout make it too risky for auto-closure.

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

Patch: wifi: mwifiex: use the subframe length when parsing A-MSDU TDLS frames
Commit: 25e5a3fe4f15e30f74eca42cbf3bcc3a3fbeda79
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=25e5a3fe4f15e30f74eca42cbf3bcc3a3fbeda79

Commit description:

mwifiex_11n_dispatch_amsdu_pkt() splits an A-MSDU with
ieee80211_amsdu_to_8023s() and walks the resulting subframes. For each
subframe it passes the subframe data pointer to
mwifiex_process_tdls_action_frame(), but pairs it with skb->len, the
length of the A-MSDU parent, instead of rx_skb->len:

	rx_skb = __skb_dequeue(&list);
	rx_hdr = (struct rx_packet_hdr *)rx_skb->data;
	if (ISSUPP_TDLS_ENABLED(priv->adapter->fw_cap_info) &&
	    ntohs(rx_hdr->eth803_hdr.h_proto) == ETH_P_TDLS) {
		mwifiex_process_tdls_action_frame(priv, (u8 *)rx_hdr,
						  skb->len);
	}

The parent is not a valid description of that buffer, and may not be
valid memory at all. ieee80211_amsdu_to_8023s() ends with

	if (!reuse_skb)
		dev_kfree_skb(skb);

and it only sets reuse_skb when the parent is linear, is not a
head_frag, and is being consumed as the *last* subframe. So when the
parent does not qualify for reuse it has already been freed, and the
read of skb->len is a use-after-free. When it is reused, skb->len is
the length of the last subframe, applied to every earlier subframe,
which over-states the buffer whenever an earlier subframe is shorter.

The callee cannot absorb a wrong length, because it derives its own
ceiling from the value it is given. Each frame type computes

	ies_len = len - sizeof(struct ethhdr) - TDLS_*_FIX_LEN;

and the element walk is then bounded entirely against that ceiling,

	for (end = pos + ies_len; pos + 1 < end; pos += 2 + pos[1]) {
		u8 ie_len = pos[1];

		if (pos + 2 + ie_len > end)
			break;

so a too-large len moves end past the end of the subframe and the walk
reads and copies beyond it. The A-MSDU layout is chosen by the sender,
which makes the difference between the last subframe and a shorter
earlier one remotely selectable. Reaching this requires TDLS support in
firmware and the TDLS ethertype on the subframe.

The other caller, mwifiex_process_rx_packet(), is correct: it passes a
pointer and a length that describe the same region of the RX buffer.

Pass rx_skb->len, the length of the subframe actually being parsed.

Fixes: 776f742 ("mwifiex: fix AMPDU not setup on TDLS link problem")
Assisted-by: Codex:gpt-5.6-sol
Assisted-by: Kimi:K3
Cc: stable@vger.kernel.org
Signed-off-by: Zhao Li <enderaoelyther@gmail.com>
Link: https://patch.msgid.link/20260728115325.19128-1-enderaoelyther@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/wireless/marvell/mwifiex/11n_rxreorder.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=25e5a3fe4f15e30f74eca42cbf3bcc3a3fbeda79

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

The original Linux kernel CVE announcement for CVE-2026-74488 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74488

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:L/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.5

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: 5
  Paranoid ActionableScore: 6

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).