[CVE-2026-98422][LOW] wifi: mac80211: reset the AP_VLAN tailroom counter on ifdown [ Upstream

[CVE-2026-98422][LOW] wifi: mac80211: reset the AP_VLAN tailroom counter on ifdown [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98422
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: wifi: mac80211: reset the AP_VLAN tailroom counter on ifdown [ Upstream
Commit: b0b32d3f163d24ea7134380666193bf398e9dc0b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b0b32d3f163d24ea7134380666193bf398e9dc0b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98422
Analysis date: Wed, 14 Oct 2026 22:31:51 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98422 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98422

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: LOW
Manual review required: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-98422	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98422 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';CWE-682;*CWE-664;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '3.3';DESCR 'The mac80211 AP_VLAN stop path failed to reset crypto_tx_tailroom_needed_cnt after the value had been increased from the parent AP during ifup. Repeated ifup and ifdown cycles could therefore accumulate a stale counter value and eventually trigger the WARN_ON_ONCE consistency check when the AP_VLAN value no longer matched the parent interface. For the CVSS the PR:L value is used in the paranoid score because a local process with delegated CAP_NET_ADMIN in a container or network namespace may be able to control AP_VLAN interface state without full host administrative access. The issue is not directly reachable through remote WiFi traffic and requires control plane operations on the local network interface. The demonstrated impact is limited to incorrect state accounting and a kernel warning with possible minor availability degradation. There is no supported UAF OOB access arbitrary write information leak or privilege escalation primitive. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 3.3 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class CLASS_C and manual review NO. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	MAYBE	REMOTE DANGER SIMPLEFIX SYZBOT DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED	-	-	checked

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

ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +0: Repeated AP_VLAN ifup operations accumulate a stale tailroom counter, but this is a bookkeeping error rather than a corruption primitive.
* +0: The demonstrated consequence is WARN_ON_ONCE. No kernel crash or strong availability impact is established.
* +0: No heap or slab OOB write, UAF, invalid free, refcount mutation, resource leak, authorization bypass, or shared-backing write is shown.
* +0: B5-R does not apply. The accumulating value is a counter, but no retry-accumulated heap OOB write or later consumption of corrupted heap state is established.
* +0: B3-PENDING does not apply because no write to shared or file-backed storage exists.
* +0: B4-PENDING does not apply because no DENY-to-ALLOW authorization decision changes.
* No privilege, race, hardware, or subsystem penalty was applied because the score is already zero and the complete privilege boundary is unresolved.
* Controlled corruption, arbitrary write, disclosure, privilege escalation, and remote reachability are not demonstrated.

3. Reachability analysis

The trigger requires repeatedly bringing an AP_VLAN interface up and down. This is a local control-plane operation rather than a remote WiFi packet trigger. Management of the interface likely involves CAP_NET_ADMIN and an existing mac80211 AP configuration, but the supplied patch does not establish which user namespace governs every required operation or whether the complete sequence is available below host-admin privilege.

Accordingly, HostAdminRequired and NamespaceScopedPrivilege remain UNKNOWN. A configured wireless AP and AP_VLAN interface are practical prerequisites. No race, narrow timing window, special retry ordering, or attacker-controlled heap layout is required.

4. Primitive and severity interpretation

The exact defect is failure to reset crypto_tx_tailroom_needed_cnt during AP_VLAN shutdown. Subsequent ifup cycles add the parent AP value again, eventually producing a mismatch detected by a sanity warning.

This is passive accounting inconsistency, not stale-object lifetime use. There is no first operation ending an object lifetime, no dangling reference, and no second release or refcount mutation. The patch does not establish that the counter indexes memory, controls a copy length, causes an OOB access, or reaches another security-sensitive operation before detection.

PrimitiveClass is NONE. The demonstrated consequence is a kernel warning. Stronger consequences such as memory corruption, host-wide DoS, information disclosure, or privilege escalation are unsupported. ImportantCandidate is therefore NO, and automatic downgrade is allowed.

5. One-sentence report phrase

Repeated AP_VLAN ifup and ifdown cycles can leave an accumulated crypto tailroom counter and trigger a mac80211 consistency warning, but no memory corruption, authorization bypass, or reliable kernel crash is established.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch fixes a bounded state-reset error with only a demonstrated WARN_ON_ONCE consequence and no unresolved security primitive.

7. Call-site confidence

Call-site confidence: medium

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

Patch: wifi: mac80211: reset the AP_VLAN tailroom counter on ifdown [ Upstream
Commit: b0b32d3f163d24ea7134380666193bf398e9dc0b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b0b32d3f163d24ea7134380666193bf398e9dc0b

Changed files:
  net/mac80211/iface.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=b0b32d3f163d24ea7134380666193bf398e9dc0b

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

The original Linux kernel CVE announcement for CVE-2026-98422 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98422

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:L/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS score: 3.3

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: unknown
  Paranoid ActionableScore: 0

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).