[CVE-2026-74336][MODERATE REGULAR] wifi: mac80211: bound S1G TIM PVB walk to the TIM element [ Upstream

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

CVE: CVE-2026-74336
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: wifi: mac80211: bound S1G TIM PVB walk to the TIM element [ Upstream
Commit: 3abc13ec3ac28c343ad7e7b7496e807b924f0edd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3abc13ec3ac28c343ad7e7b7496e807b924f0edd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74336
Analysis date: Sat, 15 Aug 2026 13:09:43 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended / Actionable Moderate watchlist
Manual review required: YES

Summary:
A nearby wireless attacker may trigger a bounded out-of-bounds read in the mac80211 S1G TIM parser by causing the PVB walker to read up to two bytes past the TIM element, with limited confidentiality concern and possible DoS but no demonstrated privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-74336 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74336

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 REGULAR
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-2026-74336	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H';CWE-125;CWE-126;*CWE-20;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '7.1';DESCR 'An out of bounds read in the mac80211 S1G TIM parser can occur because ieee80211_s1g_check_tim() passes an end pointer two bytes beyond the TIM payload to the PVB block walker. A nearby attacker in wireless range could craft an S1G TIM element so the parser reads adjacent skb or heap bytes when the TIM element is at the end of the frame. For the CVSS the PR:N is used for the paranoid score because triggering does not require local credentials on the victim and only requires adjacent wireless reachability to a vulnerable S1G receive path. The attack is not Internet reachable and should be treated as AV:A rather than AV:N because it depends on local WiFi radio proximity. Impact is at least a limited confidentiality concern from adjacent kernel buffer reads and in worst case may cause denial of service if the invalid read reaches an unmapped or hardened memory boundary. YES REQUIRES MANUAL CHECK.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended / Actionable Moderate watchlist (with actual score 4)  SKIP CVE-2026-74336 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	OOB SIMPLEFIX  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended / Actionable Moderate watchlist**

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2
  The bug is triggered by received WiFi S1G management/TIM parsing. It is not Internet-reachable, but it is adjacent-network reachable by a nearby radio attacker.
* Confidentiality impact plausible: +1
  The primitive is a bounded out-of-bounds read of up to two bytes from adjacent skb/heap data. Direct disclosure is not demonstrated, but limited parser-observable data influence is plausible.
* Rare AND difficult-to-reach subsystem/configuration: -1
  S1G / 802.11ah is much less common than ordinary WiFi paths and requires a vulnerable S1G receive path.

Paranoid additional signal:

* Availability impact realistic: +1
  Not proven as a reliable crash, but malformed frame parsing plus OOB read in kernel receive path can justify limited DoS concern for manual triage, especially with hardened/debug builds or boundary-sensitive layouts.

Not awarded:

* Generic memory corruption: +0
  This is read-only OOB, not UAF, double-free, OOB write, type confusion, or arbitrary write.
* Privilege escalation plausible: +0
  No reclaim, overwrite, callback, refcount takeover, or writable stale object primitive is shown.
* Strong DoS: +0 conservative
  The patch describes OOB read, not a demonstrated panic or reliable crash.

## 3. Reachability analysis

A nearby attacker in wireless range could potentially trigger the bug by sending a crafted S1G TIM element that reaches the mac80211 S1G parser. No local account or victim-side privileges are required, so this is closer to PR:N in CVSS terms. The path is adjacent-network only, not AV:N Internet-reachable, and practical exposure depends on S1G support and whether the affected receive path is enabled on the target device. Containers and namespaces do not materially change reachability because the trigger is external wireless frame parsing, not a local userspace API.

Call-site confidence: medium. The patch and commit message identify the parser input, the incorrect end pointer, and the downstream walker behavior, but not a demonstrated external disclosure channel or production crash.

## 4. Severity interpretation

This behaves more like an actionable Moderate / manual-review candidate than a Strong Important issue. The theoretical concern is kernel adjacent-buffer OOB read from a network-adjacent parser, which should not be auto-dismissed. Realistic exploitation evidence is limited because the read is only up to two bytes, read-only, and no direct leak, write primitive, UAF, or privilege escalation path is shown.

## 5. One-sentence report phrase

A nearby wireless attacker may trigger a bounded out-of-bounds read in the mac80211 S1G TIM parser by causing the PVB walker to read up to two bytes past the TIM element, with limited confidentiality concern and possible DoS but no demonstrated privilege escalation.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: adjacent-network reachable OOB read in a kernel packet parser, but limited to read-only access with no demonstrated leak channel, crash reliability, or LPE primitive.

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

Patch: wifi: mac80211: bound S1G TIM PVB walk to the TIM element [ Upstream
Commit: 3abc13ec3ac28c343ad7e7b7496e807b924f0edd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3abc13ec3ac28c343ad7e7b7496e807b924f0edd

Changed files:
  net/mac80211/parse.c
  include/linux/ieee80211-s1g.h

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=3abc13ec3ac28c343ad7e7b7496e807b924f0edd

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

The original Linux kernel CVE announcement for CVE-2026-74336 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74336

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:L/PR:N/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 7.1

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: 3
  Paranoid ActionableScore: 4

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 REGULAR

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).