* [CVE-2026-98406][LOW] wifi: mac80211: avoid WARN in set_bitrate_mask when sdata not in driver
@ 2026-10-16 7:42 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-16 7:42 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98406
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: wifi: mac80211: avoid WARN in set_bitrate_mask when sdata not in driver
Commit: 4ba86c44b2fcb1c3175caa2456b6d58f483446ab
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4ba86c44b2fcb1c3175caa2456b6d58f483446ab
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98406
Analysis date: Fri, 16 Oct 2026 03:42:29 -0400
ActionableScore: 1
ActionableScore lower bound: 0
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-2026-98406 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98406
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-2026-98406 LOW https://www.kernelcve.org/list/?q=CVE-2026-98406 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | 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:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-754;CWE-703;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A mac80211 interface can be marked running while it is not yet present in the driver during bringup, or after it has been removed from the driver during teardown. A local SIOCSIWRATE WEXT ioctl can then reach drv_set_bitrate_mask() and trigger the check_sdata_in_driver WARN_ONCE. No UAF, OOB access, information disclosure, or write primitive is demonstrated by this path. For the CVSS the PR:L value is used in the paranoid score because delegated CAP_NET_ADMIN, container root, or a restricted network management service may be able to reach the ioctl without having full host administration privileges. The issue is not network reachable and AC:H reflects the need to hit the interface lifecycle window. The direct impact is a warning, while systems configured with panic_on_warn may turn it into a kernel crash and denial of service. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage IMPORTANT to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC 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 LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 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 1) MAYBE REMOTE LOCK DANGER RACE SYZBOT LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
ActionableScoreLower=0
PrimitiveClass=CLASS_C
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: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* Conservative +0: the demonstrated result is WARN_ONCE after `drv_set_bitrate_mask()` detects that `sdata` is absent from the driver.
* Paranoid +1: `panic_on_warn` can convert this reachable warning into a kernel panic. This is configuration-dependent and no fatal result is demonstrated in the supplied trace.
* No race penalty: the trigger involves a bringup or teardown state window, but syzkaller reached it and the evidence does not establish a narrow or materially unreliable race.
* No privilege penalty: the complete capability boundary is unresolved. Host-admin privilege cannot be assumed merely because network-interface configuration is involved.
* No UAF, OOB access, active-state corruption, repeated release, shared-backing write, authorization bypass, or attacker-controlled write is established.
* No extra availability point was awarded because a possible `panic_on_warn` crash is the only paranoid availability consequence.
* Remote reachability, confidentiality impact, integrity impact, privilege escalation, and protected-resource access are not established.
* V32, V33, V34, B3-PENDING, B4-PENDING, and B5-R do not apply.
3. Reachability analysis
The evidenced entry point is a local WEXT `SIOCSIWRATE` ioctl. It reaches `cfg80211_wext_siwrate()`, `rdev_set_bitrate_mask()`, and then `ieee80211_set_bitrate_mask()` while the interface is marked running but lacks `IEEE80211_SDATA_IN_DRIVER`.
Wireless configuration commonly involves `CAP_NET_ADMIN`, but the supplied evidence does not resolve whether the complete bringup or teardown plus ioctl sequence requires host-owned device administration or can be performed through delegated authority. The governing capability namespace and complete namespace-scoped trigger are therefore unknown. A mac80211 interface and relevant driver state are prerequisites, but no rare-hardware penalty is justified. This is not remotely packet-triggerable.
4. Primitive and severity interpretation
The exact defect is a lifecycle-state validation omission. `SDATA_STATE_RUNNING` alone does not establish that the interface has been added to the driver. The downstream driver wrapper detects the mismatch and emits WARN_ONCE.
This is invalid-state and warning behavior, classified as CLASS_C. There is no evidence that an object has been freed, that stale storage is consumed, or that the actual driver callback corrupts state. The demonstrated consequence is a warning. The paranoid consequence is a kernel panic only when warning-to-panic behavior is enabled.
The added condition is a state-validity guard rather than an authorization check. It does not change a security decision from DENY to ALLOW and protects no identified sensitive resource. ImportantCandidate is therefore NO, and automatic downgrade is allowed.
5. One-sentence report phrase
A local SIOCSIWRATE ioctl can reach the mac80211 bitrate operation while the interface is running but absent from the driver, causing WARN_ONCE and potentially a kernel panic on systems configured with panic_on_warn.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The supplied path establishes warning-only invalid-state behavior without memory corruption, authorization bypass, cross-boundary impact, or another unresolved security primitive.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: wifi: mac80211: avoid WARN in set_bitrate_mask when sdata not in driver
Commit: 4ba86c44b2fcb1c3175caa2456b6d58f483446ab
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4ba86c44b2fcb1c3175caa2456b6d58f483446ab
Commit description:
ieee80211_set_bitrate_mask() checks if the interface is running via
ieee80211_sdata_running(), but it does not check if the interface is
still present in the driver.
When sdata is running but IEEE80211_SDATA_IN_DRIVER is not set, the
call reaches drv_set_bitrate_mask() in driver-ops.h which hits
wlan1: Failed check-sdata-in-driver check, flags: 0x0
WARNING: net/mac80211/driver-ops.h:884 at drv_set_bitrate_mask
Syzkaller triggers this via wext SIOCSIWRATE ioctl. The Call Trace shows
wext_ioctl_dispatch() in wext-core.c dispatching the ioctl, calling
ioctl_standard_call() for SIOCSIWRATE, which calls cfg80211_wext_siwrate()
in wext-compat.c. That builds a bitrate mask and calls
rdev_set_bitrate_mask() which ends up in ieee80211_set_bitrate_mask() in
cfg.c. The interface is marked running via SDATA_STATE_RUNNING but
flags is 0, so check_sdata_in_driver() fails.
When the interface is being torn down, or when wext ioctl is issued
during interface bringup before drv_add_interface() sets IN_DRIVER, the
running check passes while IN_DRIVER is clear.
Check IEEE80211_SDATA_IN_DRIVER in ieee80211_set_bitrate_mask() before
calling the driver, returning -ENETDOWN. This avoids the WARN_ONCE in
driver-ops.h and matches other cfg.c operations that bail early when not
in driver.
This change should be safe because wiphy mutex is held in
cfg80211_wext_siwrate() via guard(wiphy), and IN_DRIVER is set/cleared
under RTNL and wiphy paths in drv_add_interface() and
drv_remove_interface() in driver-ops.c, so the check is race-free
against driver add/remove. Returning -ENETDOWN is the same error other
not-running paths use and does not introduce new locking.
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=af177aa139efdd13a9da
Link: https://lore.kernel.org/all/[email protected]/
Fixes: 554a43d ("mac80211: check sdata_running on ieee80211_set_bitrate_mask")
Cc: [email protected]
Assisted-by: Hermes:muse-spark-1.2 syzkaller
Signed-off-by: Rik van Riel <[email protected]>
Link: https://patch.msgid.link/20260808104755.319c686e@fangorn
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=dcaca020ca8377e7ced0
[also add second syzbot report]
Signed-off-by: Johannes Berg <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
net/mac80211/driver-ops.h
net/mac80211/cfg.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=4ba86c44b2fcb1c3175caa2456b6d58f483446ab
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98406 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98406
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:H/PR:H/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.7
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: 0
Paranoid ActionableScore: 1
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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