* [CVE-2026-98707][MODERATE 7.0] wifi: mac80211: shut down RX BA session timer on teardown [ Upstream
@ 2026-10-19 8:52 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-19 8:52 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98707
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: mac80211: shut down RX BA session timer on teardown [ Upstream
Commit: 7bb2a5bd4f07192fca35644fab7d49a17bfbc861
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7bb2a5bd4f07192fca35644fab7d49a17bfbc861
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98707
Analysis date: Mon, 19 Oct 2026 04:52:47 -0400
ActionableScore: 6
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A nearby WiFi peer can race RX BAR processing with RX BA teardown so that a session timer is rearmed after deletion and later accesses a freed tid_rx object, causing an adjacent-network kernel use-after-free and potential host denial of service.
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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-98707 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98707
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 7.0
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
======================================================================
CVE-2026-98707 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98707 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC) 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-362;CWE-667;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'A race in mac80211 RX BA session teardown can allow an RX BAR handler to rearm session_timer after timer_delete_sync() has returned. The associated tid_rx object can then be freed through RCU while the timer remains queued, causing later timer processing or the callback to access freed kernel memory. The confirmed primitive is a use-after-free dereference in asynchronous timer processing. Impact is at least an adjacent-network denial of service through a kernel crash. Reuse of the freed allocation may also create confidentiality or integrity impact and a possible privilege escalation path, but reliable exploitation beyond DoS is not demonstrated. For the CVSS the PR:N reflects that a nearby WiFi peer may trigger the vulnerable protocol path without local access to the target host, particularly on an open or otherwise accessible wireless network. AV:A is used because the attacker must be within the relevant WiFi communication domain. AC:H is used because successful triggering depends on a race between RX BAR handling, session teardown, timer deletion, and RCU object release. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 7.5 and the production ActionableScore returned 6 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were KP and FD specialist checks stage IMPORTANT to MODERATE_KPANIC because FD false positive review allowed a downgrade. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH. The independent weaker Aegis shadow evaluated CVSS 3.1 and ActionableScore 4 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6) MAYBE REMOTE INIT UAF TIMER KPANIC DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH - - checked
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ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=6
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 6
* Conservative score: 6
* Raw paranoid score: 6
* Paranoid score: 6
* No floor or cap changed either score.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
Positive signals:
* +2 Real UAF. An RX BAR handler can retain `tid_rx` under RCU, rearm `session_timer` after `timer_delete_sync()` returns, and leave the timer queued after the RCU callback frees `tid_rx`.
* +2 Direct adjacent-network trigger. Attacker-controlled RX BAR traffic reaches the vulnerable handler from a nearby WiFi peer without local execution or host-administrator privileges.
* +1 Reliable kernel crash or strong DoS. Timer-wheel processing and the callback subsequently operate on freed kernel memory, supporting a realistic KASAN report, Oops, or kernel crash.
* +1 Broad and realistically exercised path. RX block acknowledgment aggregation and BAR processing are normal mac80211 data-plane functionality on commonly deployed WiFi systems.
Negative signals:
* No race penalty. A timing window is required, but the evidence does not establish that it is one-shot, exceptionally narrow, or impractical to retry.
* No privilege penalty. A wireless peer does not require host-administrator authority to send protocol frames after reaching the relevant WiFi relationship.
Important non-awarded signals:
* Controlled reclaim or attacker-shaped replacement contents are not demonstrated.
* Arbitrary or directed kernel write is not demonstrated.
* Structured stale-object leverage is not separately awarded because attacker influence over reclaimed `tid_rx` storage or callback-relevant replacement fields is not established.
* Attacker-influenced repeated lifetime manipulation is not awarded because the supplied call path does not prove that one peer can reliably control every session creation and teardown stage.
* Confidentiality, integrity, LPE, and callback hijacking are not scored as demonstrated consequences.
* No extra Availability point is awarded because it would duplicate the same UAF-driven crash.
* No concrete repeated release or refcount mutation exists. The bug rearms and executes a timer against freed storage rather than applying a second `put`, `free`, or refcount decrement to the same reference.
* The repeated-release paranoid bonus and FLOOR 5 repeated-release rule do not apply.
* B5-R does not apply because no retry-accumulated heap OOB write exists.
* B3-PENDING does not apply because no shared-backing or file-backed write exists.
* B4-PENDING does not apply because no authorization decision changes from DENY to ALLOW.
* V32 and V34 do not apply because checksum metadata and downstream packet-header corruption are not involved.
3. Reachability analysis
The supported attacker model is a nearby WiFi peer whose frames enter mac80211 RX processing. The peer must reach a state where an RX BA session exists and must send an RX BAR concurrently with session teardown. Association or other protocol participation may be required, but this is not host-administrator privilege and may be available on an open network or to a malicious authenticated station.
A configured mac80211 WiFi interface and active RX aggregation are deployment prerequisites. They are not evidence that the attacker needs UID 0, a host capability, or a namespace-scoped privilege. No user or network namespace capability participates in the external frame path.
The supplied evidence establishes the vulnerable interleaving but does not show every teardown caller. Peer-driven DELBA, disconnection, timeout, or local teardown may provide the competing transition. Retry practicality therefore remains partially unresolved. No hard-race penalty is applied because repeated BAR traffic and session transitions may make additional attempts possible.
This is adjacent-network exposure rather than arbitrary Internet reachability.
4. Primitive and severity interpretation
The exact primitive is an asynchronous post-lifetime use of an active structured `tid_rx` object. `timer_delete_sync()` waits for an existing timer callback but does not permanently prevent another CPU from rearming the timer. An RX BAR handler that obtained `tid_rx` before it was unpublished can therefore rearm `session_timer` after deletion. The RCU callback then frees `tid_rx`, and later timer processing consumes the freed object.
This is broader than an immediate stale cleanup dereference because a queued timer escapes teardown and later enters active kernel timer processing. It is therefore CLASS_B rather than CLASS_C. It is not CLASS_A because controlled reclaim, attacker-selected replacement contents, arbitrary kernel access, and callback control are not established.
The demonstrated consequence is kernel use-after-free with realistic crash or DoS. A stronger exploitation path through slab reuse is technically possible but remains unresolved and is not scored as proven confidentiality, integrity, or privilege-escalation impact.
ImportantCandidate is YES because this is an adjacent-network reachable active-object UAF whose stale timer survives teardown and is consumed asynchronously by a privileged kernel callback. Manual analysis of allocator reuse and callback field consumption is necessary before concluding that the issue is crash-only.
AutoDowngradeAllowed is NO because automatically reducing this to an ordinary panic-only issue would discard the unresolved exploitation leverage of an externally influenced active-object UAF. This does not itself prove Important severity.
5. One-sentence report phrase
A nearby WiFi peer can race RX BAR processing with RX BA teardown so that a session timer is rearmed after deletion and later accesses a freed tid_rx object, causing an adjacent-network kernel use-after-free and potential host denial of service.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Review the complete teardown call paths, peer control over repeated BAR and DELBA sequences, the `session_timer` callback fields consumed after free, slab reuse possibilities, and whether a malicious associated station can reliably drive both sides of the race.
7. Call-site confidence
Call-site confidence: medium
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UPSTREAM PATCH SUMMARY
======================================================================
Patch: wifi: mac80211: shut down RX BA session timer on teardown [ Upstream
Commit: 7bb2a5bd4f07192fca35644fab7d49a17bfbc861
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7bb2a5bd4f07192fca35644fab7d49a17bfbc861
Changed files:
net/mac80211/agg-rx.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=7bb2a5bd4f07192fca35644fab7d49a17bfbc861
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98707 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98707
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:L/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: unknown
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: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0
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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