* [CVE-2026-90344][MODERATE REGULAR] wifi: mac80211: disconnect on CSA to channel 0 [ Upstream
@ 2026-09-18 10:49 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-18 10:49 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-90344
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: wifi: mac80211: disconnect on CSA to channel 0 [ Upstream
Commit: 099aadb2012d7490bc584cc5075ef11cbc33f2c3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=099aadb2012d7490bc584cc5075ef11cbc33f2c3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90344
Analysis date: Fri, 18 Sep 2026 06:49:01 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90344 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90344
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.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-90344 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-90344 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:N/I:N/A:H';CWE-697;*CWE-20;CWE-754;Other CVSS 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '6.5';DESCR 'A mac80211 CSA parsing logic bug can treat channel 0 as absent information instead of an invalid target channel. A malicious or compromised AP can advertise a channel switch to channel 0 and the station may fail to disconnect as expected, which can trigger an Intel WiFi firmware crash. For the CVSS the PR:N is selected because the attacker does not need privileges on the victim and only needs adjacent WiFi reachability or control of the associated AP. The issue is adjacent network reachable rather than Internet reachable. Impact is denial of service against WiFi connectivity or the device firmware, with no evidence of kernel memory corruption or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) YES REMOTE DANGER SIMPLEFIX HARDWARE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 YES NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2. No floor or cap applied.
* Raw paranoid score: 3
* Paranoid score: 3. No floor or cap applied.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
Conservative signals:
* +1 Firmware-mediated external or adjacent influence: a malicious or compromised AP can advertise CSA to channel 0, and the effect is mediated through WiFi station handling and Intel firmware behavior.
* +1 Availability impact realistic: the supplied context states that Intel devices can hit a firmware crash, causing WiFi device or connectivity DoS.
* 0 No kernel memory corruption: the patch shows a parsing logic bug, not UAF, OOB access, arbitrary write, type confusion, or refcount misuse.
* 0 No confidentiality or integrity signal: no disclosure, unauthorized write, credential impact, or security-boundary bypass is established.
* 0 No reliable host-wide kernel crash signal: the described failure is firmware crash on Intel devices, not a demonstrated host kernel panic.
Paranoid additional signal:
* +1 Device impact may be operationally significant: a firmware crash can be more disruptive than a transient disconnect if recovery requires device reset, driver recovery, or loss of WiFi connectivity.
Non-awarded material signals:
* Remote Internet reachability not awarded. The attacker must be in adjacent WiFi range or control the associated AP.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* UAF not demonstrated.
* Privilege escalation not demonstrated.
* Extra availability beyond the device or WiFi connectivity impact is not established.
* Important-grade primitive not awarded because the bug is an invalid state handling and disconnect decision issue, not kernel corruption.
3. Reachability analysis
The realistic attacker is a nearby WiFi attacker or a malicious or compromised AP. The attacker does not need privileges on the victim host, so HostAdminRequired=NO. The trigger is adjacent-network reachable through WiFi management behavior, not through public Internet packet processing.
No namespace-scoped privilege is involved. There is no CAP_NET_ADMIN, BPF, KVM, DRM, filesystem, or local syscall control-plane requirement for the attacker in the described path.
Prior setup is that the victim must use affected mac80211 station behavior and, for the stated firmware crash consequence, an affected Intel WiFi device or firmware. This is hardware and deployment dependent, but Intel WiFi is not rare enough to apply a physical-only or rare-hardware penalty. No race or narrow timing requirement is established.
4. Primitive and severity interpretation
The exact primitive is a logic and input-validation error in CSA parsing. The old code used 0 both as a valid parsed channel value and as a sentinel for missing channel information. Since channel 0 is invalid but encodable in the CSA element, the station could treat an invalid advertised switch as absent information and fail to disconnect.
This is not an active structured UAF and not fixed stale storage. There is no concrete repeated release or refcount mutation. There is no first lifetime operation that may free an object and no second lifetime operation through a dangling reference.
PrimitiveClass=CLASS_C because the demonstrated behavior is invalid protocol state handling leading to device firmware DoS. The demonstrated consequence is WiFi firmware crash on Intel devices. The speculative consequence is broader availability disruption if recovery is poor, but no host kernel corruption, confidentiality impact, integrity impact, or LPE is supported.
ImportantCandidate=NO because no Class A or strong Class B primitive is established. AutoDowngradeAllowed=YES because the issue is Class C, DoS-oriented, and no unresolved kernel corruption or security-boundary primitive remains. Operationally this is borderline to moderate, with manual review recommended mainly due to adjacent-network reachability and device-specific firmware impact.
5. One-sentence report phrase
A mac80211 CSA parsing logic bug can let a malicious or compromised AP advertise channel 0 as a switch target, causing the station to fail to disconnect and potentially triggering an Intel WiFi firmware crash and adjacent-network DoS.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Reason: adjacent WiFi reachability and Intel firmware crash behavior make exposure and recovery device-specific, but no kernel memory corruption or privilege escalation primitive is established.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: wifi: mac80211: disconnect on CSA to channel 0 [ Upstream
Commit: 099aadb2012d7490bc584cc5075ef11cbc33f2c3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=099aadb2012d7490bc584cc5075ef11cbc33f2c3
Changed files:
net/mac80211/spectmgmt.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=099aadb2012d7490bc584cc5075ef11cbc33f2c3
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-90344 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90344
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:N/I:N/A:L
The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 6.5
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: 2
Paranoid ActionableScore: 3
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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